Vibrational sum frequency generation (VSFG) spectroscopy was applied to investigate interaction between an antibiotic, polymyxin B (PMB), and lipid monolayers at the air/water interface. The VSFG spectra in the CH stretching region observed for the monolayer of the zwitterionic (or neutral) dipalmitoylphosphatidylcholine (DPPC) spread on pure water and for the monolayer spread on a PMB aqueous solution (10(-6) M) are similar to each other, indicating the absence of interaction between the DPPC monolayer and PMB. On the other hand, the VSFG spectra of the monolayer of the anionic (or negatively charged) dipalmitoylphosphatidylglycerol (DPPG) spread on the PMB solution give rise to a prominent peak at 2850 cm(-1) due to a CH2 asymmetric stretching mode of the alkyl group, which is absent in the spectra of the DPPG monolayer on pure water, indicating that the binding of PMB to the DPPG monolayer induces the gauche defect of the alkyl group. The result suggests that the gauche defect caused by the specific binding of PMB to negatively charged parts of the cell membrane causes the increase in the fluidity and/or the permeability of the cell membrane, one of the key factors in the antibiotic activity of PMB. The VSFG spectra in the OH stretching region observed for the DPPC and DPPG monolayers on pure water are dominated by a broad band centered around 3200 cm(-1), indicating the presence of an ordered array of hydrogen-bonded water molecules associated with the hydrophilic headgroups of the monolayers. The VSFG spectra in the OH stretching region observed for the DPPC monolayer spread on the PMB aqueous solution (10(-6) M) are more or less similar to those observed for the monolayer on pure water. In contrast, the VSFG spectra of the DPPG monolayer on the PMB solution give only a very weak or almost indiscernible band near 3200 cm(-1). The binding of PMB to the interfacial region of the DPPG monolayer cancels the electrostatic field, prohibiting the formation of the ordered array of the water molecules in the interfacial region.

Infrared reflection absorption (IRA) spectra were measured for dimethyl sulfide (CH3SCH3, DMS) and methyl ethyl sulfide (CH3SCH2CH3, MES) with increasing exposure to metal substrates, Ag(1 1 0) and Cu(1 1 0), at 80 K. The spectral simulations performed by using the DFT calculation at the B3LYP/6-311++G** level indicated that (i) DMS adsorbs on the substrates with the CSC plane appreciably tilted from the surface normal, the tilt angle being about 80degrees for the adsorbate on Ag(1 1 0) and about 60degrees for the adsorbate on Cu(1 1 0), (ii) MES on Ag(1 1 0) at a submonolayer coverage state takes on the trans form with the molecular plane tilted from the surface normal by about 60degrees, and (iii) MES on Cu(1 1 0) takes the gauche form with the CSC plane almost perpendicular to the surface. The tilting of DMS is contrasted to dimethyl ether (DME) adsorbs on Ag(1 1 0) and Cu(1 1 0), where the molecular plane is perpendicular to the substrate surfaces [J. Phys. Chem. B 106 (2002) 3469]. The adsorption structures of DMS and DME are mainly determined by the coordination of the sulfur and oxygen atoms, the sulfur atom tending to coordinate to the Ag and Cu atoms through one of the 3p lone pairs (atop coordination) and the oxygen atom to the metal atoms through both of the 2p lone pairs (bridging coordination). It has been known that methyl ethyl ether (MEE) on Ag(1 1 0) takes on the trans form with the molecular plane tilted by about 45degrees and MEE on Cu(1 1 0) the gauche form with the COC plane almost perpendicular to the surface [J. Phys. Chem. B 107 (2003) 5008]. These results suggest that an attractive van der Waals interaction between the ethyl group of the adsorbates and the substrate surfaces play an important role in addition to the coordination of the sulfur and oxygen atoms in determining the rotational isomerism and orientation of MES and MEE on Ag(1 1 0) and Cu(1 1 0). (C) 2004 Elsevier B.V. All rights reserved.

Infrared reflection absorption (IRA) spectra were measured for methyl propyl ether (MPE) absorbed on Cu(110) and Ag(110) at 80 K. The IRA spectra of MPE on the substrates at sub-monolayer and full monolayer coverages exhibit simple spectral features, indicating that each adsorbate exists in a rotational isomeric form with a specific orientation relative to the substrate surface. Comparison of the IRA spectra of the adsorbates with those characteristic of MPE in bulk states taking known isomeric forms including TT, TG, GT, and GG forms (T and G are trans and gauche conformations, respectively, and the first symbol indicates the isomeric form around the O-CH2 bond and the second the form around the CH2-CH2 bond) and the simulation performed by using the density functional theory method for the IRA spectra of each isomer with varying orientations on a metal surface proved that MPE on Cu(110) takes on the GG form and MPE on Ag(110) the GT form. These forms are favorable for the coordination interaction of the oxygen atom to the metal surfaces. The spectral simulation indicated that the COC plane of the GG form tilts away from the substrate surface by about 30degrees to reduce the repulsion between the ethyl group and the Cu(110) surface, while the COC plane of the GT form tilts away from the surface by about 30degrees to a direction opposite of that of the GG form, resulting in the ethyl group with the C-C bond more or less parallel to the Ag(110) surface. From these results, it was concluded that the rotational isomerism and the orientation of the isomer on each surface are determined by the balance between the coordination interaction and an attractive (or van der Waals) interaction between the surface and the alkyl groups, the former interaction being more important on Cu(110) and vice versa on Ag(l 10).

Infrared reflection absorption (IRA) spectra were measured for methyl propyl ether (MPE) absorbed on Cu(110) and Ag(110) at 80 K. The IRA spectra of MPE on the substrates at sub-monolayer and full monolayer coverages exhibit simple spectral features, indicating that each adsorbate exists in a rotational isomeric form with a specific orientation relative to the substrate surface. Comparison of the IRA spectra of the adsorbates with those characteristic of MPE in bulk states taking known isomeric forms including TT, TG, GT, and GG forms (T and G are trans and gauche conformations, respectively, and the first symbol indicates the isomeric form around the O-CH2 bond and the second the form around the CH2-CH2 bond) and the simulation performed by using the density functional theory method for the IRA spectra of each isomer with varying orientations on a metal surface proved that MPE on Cu(110) takes on the GG form and MPE on Ag(110) the GT form. These forms are favorable for the coordination interaction of the oxygen atom to the metal surfaces. The spectral simulation indicated that the COC plane of the GG form tilts away from the substrate surface by about 30degrees to reduce the repulsion between the ethyl group and the Cu(110) surface, while the COC plane of the GT form tilts away from the surface by about 30degrees to a direction opposite of that of the GG form, resulting in the ethyl group with the C-C bond more or less parallel to the Ag(110) surface. From these results, it was concluded that the rotational isomerism and the orientation of the isomer on each surface are determined by the balance between the coordination interaction and an attractive (or van der Waals) interaction between the surface and the alkyl groups, the former interaction being more important on Cu(110) and vice versa on Ag(l 10).

Sum frequency generation (SFG) spectroscopic studies were performed on the structures of the Langmuir-Blodgett monolayers of palmitoyl-L and DL-ornithines (PO) and parmitoyl-L and DL-lysines (PL) on a quartz substrate and those of the monolayers of PO and PL at the air-water interface. The analyses of the SFG spectra based on spectral simulations indicated that (i) the NH groups in the monolayers of L-PO and L-PL on the quartz substrate are more or less parallel to the substrate taking two different orientations of ±ca. 30° with respect to the drawing direction of the samples employed by preparation processes, (ii) on increasing the surface pressures of the L-PO and L-PL monolayers at the air-water interface the tilt angles of the CH3 group with respect to the surface normal decreases appreciably, and (iii) the tilt angle of the CH3 group in the DL-PL monolayer is appreciably smaller than that of the L-PL monolayer, suggesting the existence of a specific interaction between the L- and D-enantiomers in the DL-PL monolayer at the air-water interface.

To understand the mechanism of thermochromic phase transition of a J-aggregate monolayer of a merocyanine dye (MD, 3-caboxymethyl-5-[2-(3-octadecyl-benzothiazolin-2-ylidene)ethylidene]rhodanine) on aqueous subphases containing Mg2+ and Cd2+ ions, the molecular vibrational investigation was performed by using external infrared (IR) reflection absorption spectroscopy. The in situ observation indicates that, on increasing the subphase temperature from 19.5 to 34.5 degreesC, IR bands observed at 1177 and 1126 cm(-1) for the J-aggregate monolayer shift to 1188 and 1146 cm(-1), respectively; the shift is reversible and exhibits a thermal-hysteresis. These spectral changes correspond well to the thermochromic behavior of the visible absorption band of the J-aggregate (J-band), where the J-band shift is observed between 620 and 595 nm. The ab initio calculation of the normal modes were carried out on the MD molecule to assign the IR bands near 1183 and 1136 cm(-1), indicating that they are attributed by the vibrational modes of the carboxymethyl group coupled with the modes of the thioketon group of the rhodanine ring, the conjugated backbone of the dye, and the benzothiazole C Group. Both spectroscopic and computational results suggest that the transition from the phase of the J-band at 620 nm to that of the J-band at 595 nm is characterized by the exchange of the metal ion from Mg2+ to Cd2+ interacting with the MD molecule through the carboxylate group of the carboxymethyl group, and the exchange of metal ion induces the shift of the IR bands as well as the J-band.

To understand the mechanism of thermochromic phase transition of a J-aggregate monolayer of a merocyanine dye (MD, 3-caboxymethyl-5-[2-(3-octadecyl-benzothiazolin-2-ylidene)ethylidene]rhodanine) on aqueous subphases containing Mg2+ and Cd2+ ions, the molecular vibrational investigation was performed by using external infrared (IR) reflection absorption spectroscopy. The in situ observation indicates that, on increasing the subphase temperature from 19.5 to 34.5 degreesC, IR bands observed at 1177 and 1126 cm(-1) for the J-aggregate monolayer shift to 1188 and 1146 cm(-1), respectively; the shift is reversible and exhibits a thermal-hysteresis. These spectral changes correspond well to the thermochromic behavior of the visible absorption band of the J-aggregate (J-band), where the J-band shift is observed between 620 and 595 nm. The ab initio calculation of the normal modes were carried out on the MD molecule to assign the IR bands near 1183 and 1136 cm(-1), indicating that they are attributed by the vibrational modes of the carboxymethyl group coupled with the modes of the thioketon group of the rhodanine ring, the conjugated backbone of the dye, and the benzothiazole C Group. Both spectroscopic and computational results suggest that the transition from the phase of the J-band at 620 nm to that of the J-band at 595 nm is characterized by the exchange of the metal ion from Mg2+ to Cd2+ interacting with the MD molecule through the carboxylate group of the carboxymethyl group, and the exchange of metal ion induces the shift of the IR bands as well as the J-band.

A density functional theory (DFT) calculation was performed on the cluster models of ethylene on Cu(110), Ag(110), and Pd(110) to clarify the correlation between the IR spectra of the adsorbate and the modes of ethylene-surface interaction. The metal surfaces were modeled by two- or three-layered clusters consisting of 13-34 metal atoms. Four kinds of adsorption sites were considered: atop bonding sites with the CC bond parallel and perpendicular to the (1 (1) over bar0) direction (ST and LT sites), a short bridge site with the CC bond parallel to the (1 (1) over bar0) direction (SB site), and a long bridge site with the CC bond perpendicular to the (1 (1) over bar0) direction (LB site). The results of calculations for three-layered models consisting of more than 20 metals could be compared reasonably with the experimental data. The comparison indicated that (i) upon increasing surface coverage, ethylene on Cu(110) converts its adsorption site from an SB to an ST site, (ii) ethylene adsorbs at an LT site of Ag(110), and (iii) ethylene on Pd(110) takes on an ST site. These conclusions are consistent with those derived from STM and other spectroscopic measurements including UPS and NEXAFS, indicating that the DFT calculation on the cluster models is efficient for the analysis of the IR spectra of ethylene adsorbed on metal surfaces, which delineates the adsorption modes. The contribution of donation and back-donation of electrons to the ethylene-metal bonding was estimated by calculating the projections to the pi-bonding and pi*-antibonding orbitals of the isolated ethylene in the adsorbed geometries. The results proved that both the pi donation and pi* back-donation make appreciable contributions to the ethylene-surface interaction on Cu(110), whereas the pi* back-donation is negligible in the ethylene-Ag(110) interaction. It was suggested that the frequency increase of the CH2 out-of-plane wagging vibration from that of the free ethylene observed for ethylene on Ag(110) is a measure of the contribution of the pi donation to the ethylene-surface interaction.

Infrared reflection absorption (IRA) were measured for the Langmuir-Blodgett (LB) films of palmitoyl-lysine (PL) and palmitoyl-omithine (PO) with various mixing ratios of the L- and D-enantiomers. The introduction of the D-enantiomers to the LB films consisting of the L-enantiomers in PO-LB does not cause any frequency shifts of the amide I and II bands of the peptide groups in PO-LB, while the introduction causes appreciable frequency changes in PL-LB. The IRA spectra of the LB films soaked in D2O indicated a much higher H/D exchange rate of the peptide groups for PL-LB than that for PO-LB. These results proved the existence of a more flexible molecular assembly in PL-LB compared to that in PO-LB. The SFG spectrum of PL-LB (D/L = 0/10) gives rise to peaks at 3220 and 3160 cm(-1), which are absent in the SFG spectra of PO-LB (D/L = 0/10). The peaks are ascribable to water molecules in an ordered arrangement, which play as a channel for the H/D exchange process. The bound water molecules render PL-LB more hydrophilic than PO-LB, which explains the fact that the PL-LB forms a Z-type structure and PO-LB a Y-type structure. (C) 2002 Elsevier Science B.V. All rights reserved.

Infrared spectra were measured at 80 K for dimethyl ether (CH3OCH3, DME) and dimethyl ether-d(6) (CD3OCD3, DME-d(6)) with increasing amounts of exposures to metal substrates, Ag(110), Cu(110), and their atomic oxygen-reconstructed surfaces, p(2 x 1)O-Ag(110) and p(2 x 1)O-Cu(110). At relatively lower surface coverages, the IR spectra of DME on Ag(110) and Cu(110) in the 1500-800 cm(-1) region give rise to IR bands mainly ascribable to A(1) species, including symmetric COC stretching (v(s)(COC)) bands at 903 cm(-1) on Ag(110) and 895 cm(-1) on Cu(110), while at nearly saturation coverages, the adsorbate gives IR bands ascribable to B-1 and/or B-2 species in addition to the A(1) bands with the v(s)(COC) band discretely sifted to 915 cm(-1) on Ag(110) and to 901 cm(-1) on Cu(110). Similar distinct spectral changes were observed also for DME and DME-d(6) on the reconstructed surfaces. The stepwise spectral changes were interpreted in terms of a conversion from a state of DME with the C-2 axis almost perpendicular to the surfaces to a state with the C-2 axis tilted away from the perpendicular orientation. Fermi resonance effects cause stepwise but complicated spectral changes in the CH3 stretchin g vibration region of DME during the conversion. The changes strongly depend on the kind of the substrates, in contrast to the spectral changes in the 1500-800 cm(-1) region, suggesting that the analyses of Fermi resonances can delineate subtle differences in the DME/substrate interaction modes among the substrates. Density functional theory (DFT) molecular, orbital calculations were carried out on the cluster models of DME/Cu(110), where the oxygen atom of DME is coordinated to two copper atoms in the surface of metal clusters consisting of 12 copper atoms in the first layer and six copper atoms in the second layer. The results of calculations reproduce the observed frequencies appreciably well, substantiating the coordination interaction model.

Infrared spectra were measured at 80 K for dimethyl ether (CH3OCH3, DME) and dimethyl ether-d(6) (CD3OCD3, DME-d(6)) with increasing amounts of exposures to metal substrates, Ag(110), Cu(110), and their atomic oxygen-reconstructed surfaces, p(2 x 1)O-Ag(110) and p(2 x 1)O-Cu(110). At relatively lower surface coverages, the IR spectra of DME on Ag(110) and Cu(110) in the 1500-800 cm(-1) region give rise to IR bands mainly ascribable to A(1) species, including symmetric COC stretching (v(s)(COC)) bands at 903 cm(-1) on Ag(110) and 895 cm(-1) on Cu(110), while at nearly saturation coverages, the adsorbate gives IR bands ascribable to B-1 and/or B-2 species in addition to the A(1) bands with the v(s)(COC) band discretely sifted to 915 cm(-1) on Ag(110) and to 901 cm(-1) on Cu(110). Similar distinct spectral changes were observed also for DME and DME-d(6) on the reconstructed surfaces. The stepwise spectral changes were interpreted in terms of a conversion from a state of DME with the C-2 axis almost perpendicular to the surfaces to a state with the C-2 axis tilted away from the perpendicular orientation. Fermi resonance effects cause stepwise but complicated spectral changes in the CH3 stretchin g vibration region of DME during the conversion. The changes strongly depend on the kind of the substrates, in contrast to the spectral changes in the 1500-800 cm(-1) region, suggesting that the analyses of Fermi resonances can delineate subtle differences in the DME/substrate interaction modes among the substrates. Density functional theory (DFT) molecular, orbital calculations were carried out on the cluster models of DME/Cu(110), where the oxygen atom of DME is coordinated to two copper atoms in the surface of metal clusters consisting of 12 copper atoms in the first layer and six copper atoms in the second layer. The results of calculations reproduce the observed frequencies appreciably well, substantiating the coordination interaction model.

External infrared reflection spectroscopy was applied to study a phase transition of the monolayer of octadecylurea (OU) at the air-water interface. Upon compression at a constant; temperature (6 degrees C in this study) the monolayer undergoes the transition from a condensed phase (beta phase) with a larger limiting area (0.250 nm(2)/molecule) to another condensed phase (alpha phase) with a smaller limiting area (0.195 nm(2)/ molecule). The formation of the a phase and the phase transition accompany discrete IR spectral changes in the V-as(CH2), v(s)(CH2), amide I, amide II, and delta(NH2) vibration regions. The spectral changes indicated that (i) upon compression of the monolayer to form the beta phase the alkyl side chain is converted from an irregular state containing gauche conformations to an ordered one consisting of the all-trans conformation and at the same time the peptide bond in the head group is transformed from a fully hydrated, state to a hydrogen-bonded one and (ii) upon further compression to the alpha phase and/or a collapsed slate the alkyl side chains are changed again to the irregular state and a part of the peptide bonds is converted to the hydrated state. These results are contrasted with the case of the monolayer of N-methyl-N-octadecylurea (MOU) at the air-water interface, which gives the amide I and delta(NH2) bands characteristic of a fully hydrated state irrespective of the molecular area. Thus, the IR spectral changes provided direct; proofs for the explanation that the endothermic fiat-order beta -> alpha phase transition of the OU monolayer takes place through a partial collapse of the two-dimensional ordered array consisting of the hydrogen-bonded network between the peptide bonds.

Infrared reflection absorption spectra in the CW, out-of-plane wagging (omega(CH(2))) vibration region were measured for ethylene (C(2)H(4)) adsorbed on Ag(110) as well as on the oxygen-induced p(n x 1) reconstructed surfaces of Ag(110) (n = 2, 3, 4 and 6) at 80 K. C(2)H(4) on Ag(110) gives a main peak at 955 cm(-1), while on p(2 x 1)O-Ag(110) it exhibits a broad features of at least four components (997, 984, 970 and 954 cm(-1)) at saturation coverage. C(2)H(4) on p(n x 1)O-Ag(110) (n = 6, 4, 3) gives rise to a 972-976 cm(-1) band at low exposures, shifting to 966-970 cm(-1) at saturation coverage. The spectral changes are interpreted by assuming a pair of adsorption sites on both sides of the added Ag-O rows of the reconstructed surfaces. (C) 1999 Elsevier Science B.V. All rights reserved.

Infrared reflection-absorption spectra in CN stretching, CH(2) out-of-plane wagging and CH(2) twisting vibration regions were measured for acrylonitrile (CH(2)-CHCN) exposed to Ag(111) and Ag(110) in increasing amounts at 77 K. The adsorbate on Ag(lll) takes on a series of discrete adsorption states; i.e., an isolated state, associated states, and ordered and amorphous multilayer states. The adsorbate on Ag(110) at lower exposures is in a state with the CN group weakly coordinated to a silver atom (or silver atoms). The adsorbate on Ag(110) takes the associated state and the amorphous multilayer at larger exposures. On raising the temperature to 96 K, the amorphous states on both Ag(lll) and Ag(110) are converted to the ordered multilayer. The desorption temperature of the ordered multilayer is below 99 K for Ag(110), while the temperature is above 107 K for Ag(lll); the result indicates the effect of the surface morphology on the stability of the ordered state. (C) 1999 Elsevier Science B.V. All rights reserved.

External infrared reflection absorption spectroscopy was used to study the carboxylate-counterion interactions and changes in these interactions during the photopolymerization of a long-chain diacetylene monocarboxylic acid, 10,12-pentacosadiynoic acid (DA), at air-water interfaces in the presence of divalent metal ions, Ba2+ (pH 7.7), Cd2+ (pH 6.8), and Pb2+ (pH 6.0). Upon reducing the molecular area (0.80 → 0.18 nm2/molecule), the DA monolayer on each subphase exhibited discrete frequency changes of an IR band due to a carboxylate antisymmetric stretching vibration (vas(COO-)), indicating discrete changes in the coordination and/or association states of the carboxylate groups. Ab initio molecular orbital calculations were applied to confirm the empirical relationships between the frequency differences of the asymmetric and symmetric stretching bands of the carboxylate group and the modes of coordination of the group to metal ions. On the basis of the relationships, it was proposed that, when the molecular area is reduced, the carboxylate group in the DA monolayer on the Ba2+ subphase changes its coordination mode from a bridging state to a bidentate one, while the carboxylate group in the DA monolayer on the Cd2+ subphase keeps a bidentate coordination state. It was also suggested that the DA monolayer on the Pb2+ subphase exhibits a coordination change from a bridging to bidentate state upon compression. IR spectral changes in the vas(COO-) and vs(COO-) regions observed during UV-irradiation-induced polymerization of the DA monolayers were similar to the IR spectral changes observed by compressing the monolayers without irradiation. The results indicated that the polymerization induces more densely packed states of the carboxylate groups in the monolayers. © 1999 American Chemical Society.

A combined method of multiple-reflection and optical-wave-guide Raman spectroscopies was proposed for studying the electric-field-induced reorientation of a surface-stabilized ferroelectric liquid crystal (FLC) cell. The method allowed us to measure selectively Raman scattering (RS) spectra from the FLC in a bulk phase and those from the FLC near an SiOx alignment layer. Time-resolved RS spectra from the two parts were measured by applying step-wise external electric fields, indicating that the FLC near the alignment layer exhibits a retarded response to the field compared to that in the bulk phase. The results proved the usefulness of the proposed method. (C) 1998 Elsevier Science B.V. All rights reserved.

Infrared (IR) external reflection absorption spectroscopy was applied to study the structure and its change associated with iodine doping of a Langmuir-Blodgett (LB) film of a tetrathiafulvalene (TTF) derivative, 1,3-dithiole-4-carboxylic acid-2-(1,3-dithiol-2-ylidene)hexadecyl ester (HDTTF, Figure 1), prepared on a silicon wafer. The incidence angle (phi) dependence of the p- and s-polarized IR external reflection spectra were measured and analyzed by a theoretical calculation of reflection absorbance (A(p) and A(s)) as a function of the tilt angle of the transition moment of each IR band with an assumed complex refractive index. The results indicated that the LB film before doping consists of cis and trans structures, which have the C=O bonds with cis and trans configurations, respectively, with respect to the neighboring C=C bond of the TTF ring. The TTF ring in both structures are almost perpendicular to the substrate surface with the central C=C bond parallel to the surface. After iodine doping the LB film consists of the cis structure and gives rise to charge-transfer-induced vibronic bands at 1352 and 1252 cm(-1). The analyses of the phi dependence of A(p) of these bands proved that the transition moments of both bands make a tilt angle of about 70 degrees with respect to the surface normal of the substrate, which is consistent with a face-to-face stacking of the TTF rings nearly perpendicular to the surface and the high conduction parallel to the substrate.

Infra-red reflection absorption (IRA) spectra were measured at 80 K under ultra-high vacuum conditions for acrolein adsorbed on two kinds of gold films
Au(111) and polycrystalline gold surfaces. Upon increasing the amount of exposure from 0.02 to 200 L (1 L=1 × 10 6Torr·s), the adsorbate at Au(111) gave rise to a series of sharp IRA bands due to a CH2 out-of-plane wagging vibration [ω)(CH2)] successively, indicating discrete adsorption states, i.e. 964 (type 1)→978(type 1)→978(type 2)→1003 cm-1(type 3). All these states have the molecular plane parallel to the surface
type 1 is in an isolated state, and type 2 is in an associated state with a two-dimensional arrangement, whereas type 3 forms an ordered multilayered structure. Type 1′ was tentatively assigned either to a trapped state at step sites or to an associated state forming small oligomers at the surface. Only type 3 gives rise to IRA bands due to ν(C=O), which appears at 1677 cm-1 as a singlet at relatively small exposure levels and splits into doublets, giving the 1686 and 1672 cm-1 components at 2.0 L. The doublets were explained as being due to a crystal field splitting, which conforms to the fact that the adsorbate forms an ordered three-dimensional arrangement. The IRA spectrum of type 3 is readily converted to that of a more stable polycrystalline state upon increasing the temperature from 80 to 100 K. Thus, type 3 is a thermodynamically metastable state. Acrolein adsorbed on a polycrystalline gold film assumes an amorphous state in the exposure level of 0.06-4.8 L, giving broad IRA bands due to ν(C=O) and ω(CH2) in the 1686-1699 and 974-991 cm-1 regions, respectively. The IRA spectra of acrolein adsorbed on Ag(111) were also measured, which indicated that the adsorbates exist in a less ordered state than those on Au(111), although a multilayered structure gives IRA features that are almost identical with those of type 3. © 1998 Elsevier Science B.V. All rights reserved.

Infra-red reflection absorption (IRA) spectra were measured at 80 K under ultra-high vacuum conditions for acrolein adsorbed on two kinds of gold films: Au(111) and polycrystalline gold surfaces. Upon increasing the amount of exposure from 0.02 to 200 L (1 L=l x 10(-6) Torr.s), the adsorbate at Au( 111) gave rise to a series of sharp IRA bands due to a CH2 out-of-plane wagging vibration [omega(CH2)] successively. indicating discrete adsorption states, i.e. 964 (type 1)-->978(type 1')-->992(type)-->1003 cm(-1)(type 3). All these states have the molecular plane parallel to the surface: type I is in an isolated state, and type 3 is in an associated state with a tn two-dimensional arrangement, whereas type 3 forms an ordered multilayered structure. Type 1' was tentatively assigned either to a trapped state at step sites or to all associated state forming small oligomers at the surface. Only type 3 gives rise to IRA bands due to nu(C=O). which appears at 1677 cm(-1) as a singlet at relatively small exposure levels and splits into doublets, giving the 1656 and 1672 cm(-1) components at 2.0 L. The doublers were explained as being due to a crystal field splitting, which conforms to the fact that the adsorbate forms an ordered three-dimensional arrangement. The IRA spectrum of type 3 is readily converted to that of a more stable polycrystalline state upon increasing the temperature from 80 to 100 K, Thus. type 3 is a thermodynamically metastable state. Acrolein adsorbed on a polycrystalline gold film assumes an amorphous state in the exposure level of 0.06-4.8 L, giving broad IRA bands due to nu(C= O) and omega(CH2) in the 1686-1699 and 974-991 cm(-1) regions, respectively. The IRA spectra of acrolein adsorbed on Ag(111) were also measured, which indicated that the adsorbates exist in a less ordered state than those on Au(111). although a multilayered structure gives IRA features that are almost identical with those of type 3.

Total internal reflection (TIR) Raman scattering spectroscopy was performed using a cell combined with a high index hemicylindrical substrate and a glass plate with obliquely evaporated SiO alignment layers to study an electric-field-induced reorientation process of 4-n-hexyl-4'-cyanobiphenyl (6CB) in a nematic phase. Two types of cells having different director configurations were studied; one has the orientation of the director parallel to the axis of the hemicylinder (s-configuration) and the other the director perpendicular to the axis (p-configuration). Squared relative Raman scattering tensor components of the LC layer were determined by analyzing the polarized TIR Raman spectra observed for the cells. Time-resolved TIR Raman measurements were performed on the p-configuration cell under application of squared electric fields (duration = 10 ms, repetition rate = 10 and 5 Hz, amplitude = 3-8 V) by using a pulsed Nd-YAG laser (ex = 532 nm, pulse width = about 15 ns). The results elucidated characteristics of the electric field-induced reorientation dynamics of a layer of the LC molecules (with a thickness of about 50 nm) adsorbed on the evaporated SiO film: (i) Upon application of the electric field with the amplitudes of 3-5 V the director of the surface layer keeps its original orientation for a certain period, although the director of the bulk phase immediately responds to the fields; the period becomes longer as the amplitude decreases, being ca. 4 ms for the amplitude of 5 V and about 6 ms for 3 V: (ii) After switching off the electric fields the surface layer exhibits a rapid recovery process with the time constant for 3-6 ms, which is appreciably shorter than that of the bulk phase of almost 350 ms (measured under application of the squared electric field of 9 V). An elastic interaction force within the former.

Total internal reflection (TIR) Raman scattering spectroscopy was performed using a cell combined with a high index hemicylindrical substrate and a glass plate with obliquely evaporated SiO alignment layers to study an electric-field-induced reorientation process of 4-n-hexyl-4'-cyanobiphenyl (6CB) in a nematic phase. Two types of cells having different director configurations were studied; one has the orientation of the director parallel to the axis of the hemicylinder (s-configuration) and the other the director perpendicular to the axis (p-configuration). Squared relative Raman scattering tensor components of the LC layer were determined by analyzing the polarized TIR Raman spectra observed for the cells. Time-resolved TIR Raman measurements were performed on the p-configuration cell under application of squared electric fields (duration = 10 ms, repetition rate = 10 and 5 Hz, amplitude = 3-8 V) by using a pulsed Nd-YAG laser (ex = 532 nm, pulse width = about 15 ns). The results elucidated characteristics of the electric field-induced reorientation dynamics of a layer of the LC molecules (with a thickness of about 50 nm) adsorbed on the evaporated SiO film: (i) Upon application of the electric field with the amplitudes of 3-5 V the director of the surface layer keeps its original orientation for a certain period, although the director of the bulk phase immediately responds to the fields; the period becomes longer as the amplitude decreases, being ca. 4 ms for the amplitude of 5 V and about 6 ms for 3 V: (ii) After switching off the electric fields the surface layer exhibits a rapid recovery process with the time constant for 3-6 ms, which is appreciably shorter than that of the bulk phase of almost 350 ms (measured under application of the squared electric field of 9 V). An elastic interaction force within the former.

Total internal reflection (TIR) Raman scattering spectroscopy was performed using a cell combined with a high index hemicylindrical substrate and a glass plate with obliquely evaporated SiO alignment layers to study an electric-field-induced reorientation process of 4-n-hexyl-4'-cyanobiphenyl (6CB) in a nematic phase. Two types of cells having different director configurations were studied; one has the orientation of the director parallel to the axis of the hemicylinder (s-configuration) and the other the director perpendicular to the axis (p-configuration). Squared relative Raman scattering tensor components of the LC layer were determined by analyzing the polarized TIR Raman spectra observed for the cells. Time-resolved TIR Raman measurements were performed on the p-configuration cell under application of squared electric fields (duration = 10 ms, repetition rate = 10 and 5 Hz, amplitude = 3-8 V) by using a pulsed Nd-YAG laser (ex = 532 nm, pulse width = about 15 ns). The results elucidated characteristics of the electric field-induced reorientation dynamics of a layer of the LC molecules (with a thickness of about 50 nm) adsorbed on the evaporated SiO film: (i) Upon application of the electric field with the amplitudes of 3-5 V the director of the surface layer keeps its original orientation for a certain period, although the director of the bulk phase immediately responds to the fields; the period becomes longer as the amplitude decreases, being ca. 4 ms for the amplitude of 5 V and about 6 ms for 3 V: (ii) After switching off the electric fields the surface layer exhibits a rapid recovery process with the time constant for 3-6 ms, which is appreciably shorter than that of the bulk phase of almost 350 ms (measured under application of the squared electric field of 9 V). An elastic interaction force within the former.

　強誘電性液晶（FLC）セルは、双安定性、高速応答性、広視野角など点で、現在広く用いられているネマティック液晶セルに比して種々の優れた性能を示し、液晶ディスプレイの広い応用が期待されている。しかしながら配向膜表面とFLCとの相互作用がいかにして双安定性を発現するか、また、その相互作用がFLCの電場配向過程にどのように影響するか、などの問題点の解明は、FLCセルの性能向上に不可欠であるにもかかわらずきわめて不完全な状態にある。この主な原因は、従来の測定手段がFLCセルの電場応答性についてセルの厚さ方向について選択的な情報を与えることが出来なかったことに由来している。本研究では、ナノ秒の高い時間分解能を有するラマン分光性とATR（Attenuated Total Reflectiion）法を組み合わせて、励起レーザー光の入射角度によってセルの厚さ方向の電場プロファイルを変化させつつ時間分解ラマンスペクトルを測定して、FLCの印加電場に対する応答性をセルの厚さ方向について詳細に調べることを目指した。また、顕微測光方式を採用して二次元的な情報も収集して、FLCの電場応答性の三次元解析も行った。　FLCにはフェニルピリミジン骨格をもつ試料を用い,高屈折率円筒型プリズムの底面（15mm×15mm）にITO電極/配向膜/FLC/配向膜/ITO電極の層状構造を持つセルを作製した。配向膜としてSio斜方蒸着膜を採用した場合、ダイレクターの方向がプリズム軸に平行な配向と45°傾いた２つの安定構造を示した。+10 ― -10Vの交番短形電位印加による双安定状態間の転移の過程にともなうFLCのラマンバンド強度の時間変化を、励起レーザー光のプリズムに対する入射角度を全反射角前後で変化させつつ測定し、セルの厚さ方向についての光学的異方性変化を仮定して理論的シュミレーションし解析した。その結果、配向膜近傍のFLCの時間応答性はバルク相に比してきわめて遅いこと、一方印加電場を切るとバルク相の一部がその双安定構造を速やかに失うことなどの新しい知見を得ることが出来た。

研究成果の概要を以下にまとめる。(各項目の［ ］内は文献番号)(1) 　多結晶蒸着金およびAu(111)表面におけるアクロレインの吸着構造に関する研究　[1]超高真空下におけるAu(111)表面でのアクロレイン分子の吸着構造を高感度赤外反射吸収スペクトル（IRAS）法を用いて調べ、吸着量の増大に伴なう孤立→会合→飽和吸着の各段階における吸着様式、配向、分子間相互作用の詳細を明らかに、IRAS法が平面分子の二次元的配列構造の解明にきわめて有力であることを示した。(2)　Au(111)およびAg(111)表面における1,3―ブタジエンの吸着構造に関する研究　[2]　超高真空下におけるAu(111)表面でのアクロレイン分子の吸着構造をIRAS法を用いて調べ、吸着量の増大に伴なう孤立→会合→一層飽和→多層吸着の各段階における吸着様式、配向、分子間相互作用、分子構造の詳細を明らかにした。特に、熱力学的に不安定なs-cis型が数層吸着状態でのamorphous相に局在することを示した。(3)　Ag(110)面とその原子状酸素再構成面におけるエチレンの吸着構造に関する研究　[3]Ag(110)面とその原子状酸素による一連の再構成表面（p(nx1)-0-Ag(110)、n＝2, 3, 4, 6）でのエチレン分子の吸着様式の相違を、導入量によるIRASスペクトル変化を測定・解析することによって調べた。その結果、エチレンがAg-0鎖に選択的に吸着するとする従来の考え方は誤りで、吸着サイトはAg-0鎖の両側で対を形成し、エチレン分子の導入量の増加によりサイト対の一方が占められた状態（α―状態）と両方が占められた状態（β―状態）が段階的に生じることを明らかにした。(4)　Ag(111)およびAg(110)面におけるアクリロニトリルの吸着構造に関する研究　[4]　Ag(111)およびAg(110)面におけるアクリロニトリル分子のIRASスペクトルの測定・解析結果をもとに、各表面における吸着様式、構造、配向、分子間相互作用、二次元的秩序構造を明らかにした。調べた。その結果、(ii)アクリロニトリル分子がAg(110)面ではCN基を介して弱く配位し傾いた配向をとるのに対し、Ag(111)面では分子面を基板に対しほぼ平行にして物理吸着しているこて安定であること、などが明らかになった。

ジアセチレン誘導体である10,　12-pentacosadiynoic acid（以下　ＤＡ）のLangmuir-Blodgett膜を島状銀蒸着膜（膜厚６nm）と平滑銀蒸着膜（膜厚　100nm）に作製して、それらの紫外光照射による重合過程を表面増感共鳴ラマン（ＳＥＲＲＳ）分光法と共鳴ラマン（ＲＲＳ）分光法を用いて調べた。その結果、(i)ＤＡ単分子膜（Ｌ＝1）においても、ＤＡ（Ｌ≧3）累積膜の場合と同様に、重合にともない、生成ポリジアセチレン（以下ＰＤＡ）の規則―不規則転移が見られること、(ii)ＳＥＲＳ活性な島状銀蒸着膜上での光重合速度が、ＳＥＲＳ不活性な平滑銀蒸着膜上に比して著しく増大することを見出した。以前にわれわれは、ＤＡ累積膜の光重合過程について、共役鎖長の長いＰＤＡの規則構造が重合の進行とともに不安定になって共役鎖長の短い不規則構造に転移する機構を提案したが、(i)は、この規則―不規則転移が２次元的な現象であることを証明した。また、(ii)の原因を明らかにするために、銀蒸着膜の厚さやスペーサーＬＢ膜を挿入して蒸着膜とＤＡ―ＬＢ膜間距離を変化させつつ光重合速度を調べた。その結果、光重合速度の増大が、島状銀蒸着膜における表面プラズモン励起を介したまったく新しい表面増感機構によることを明らかにした。研究成果の発表1997年K.Itoh, M.Yamamoto, N.Furuyama and A.Saito, Mikrochim. Acta, 14，33. “Infrared reflection absorption spectroscopic study on photochemical processes in langmuir-Blodgett films.”1997年Y. Misono, Y.Okata, T.Morikawa and K. Itoh, J. Electroanal. Chem., 436， 203.“Resonance Raman and absorption spectroscopic studies on the electrochemical oxidation processes of 3, 3', 5, 5'-tetramethylbenzidine.”1998年E.Shirai, Y.Urai and K.Itoh, J.Phys. Chem. 102，3765. Surface-enhanced photopolymerization of a diacetylene derivative in Langmuir-Blodgett films on a silver island film.

　1999年度開催予定の第12回フーリエ変換分光学国際会議(略称ICOFTS-12)を早稲田大学国際会議場で開くために種々の準備活動を行なった。以下にその主なものを記す。　(1)第10回フーリエ変換分光学国際会(1995年8月、ブダペスト)への開催計画案の提出と承認　1996年8月、ブダペストで開催されたICOFTS-10における国際組織委員会に、伊藤(早大理工)、田隅(東大理)が出席し、1999年度のICOFTS-12の東京(早稲田大学国際会議場)開催計画案を提出し、その趣旨を説明した。その結果、委員会の承認を得て、1999年度ICOFTS-12の早稲 田大学国際会議場での開催が正式に承認された。　(2)組織委員会の設立　国内外の大学・企業・研究所におけるこの関連分野の主な研究者からなる組織委員会を発足させ、その第1回目の会合を1996年5月に開催し、1.国際会議の基本方針と性格付け、2.会期、3.プログラム内容、4.財政的基盤の確立などについて話し合った。　(3)企業関係の協力会の設立　ICOFTS-12を成功させるためには、大学や公官庁の研究所ばかりでなく企業の研究者の積極的な参加が是非必要である。また財政的基盤の確立には、企業の援助が不可欠である。そこで、1996年10月から国内外のフーリエ変換分光計の製作会社および関連分野の企業研究者によるICOFTS-12開催のための協力会設立の準備を進め、同年12月に正式に発足させた。現在、24社から協力の参加を得て、研究会・講演会の開催などを通じて密接な情報の交換をはかるべく準備を進めている。　(4) First Circular原稿の作成　田隅三生(現埼玉大理)をChairmanとする国際的なプログラム委員会とJ.A.de Haseth教授(ジョージア大学、米）をChairmanとするSteering委員会委員の人選を進め、First Circularの原稿を作成し、現在印刷の準備を進めている。

上記の課題について，次の二項目の研究を進め下記の成果を得た。（1）フーリエ変換赤外外部反射分光法によるLangmuir単分子膜の振動スペクトル測定装置の試作 全面をテフロンコートした3cm×10cm×0.5cmの水槽，アクチュエータによって位置の自動制御可能なバリアー，および小型Whilehelmy Balanceとを組み合わせて水面上単分子膜（以下L膜）の赤外外部反射（以下EIR）スペクトル装置を作成し，フーリエ変換赤外分光器に設置して，水槽におけるpH値と共存金属の種類を変化させつつアラキジン酸L膜のEIRスペクトルを測定した。その結果，この方法によって，4000-700cm-1の領域で十分なS/N比のEIRスペクトル測定が可能なことを確かめるとともに，アラキジン酸L膜の表面圧の上昇に伴う液相→固相転移における水素結合状態の変化についての直接的な知見を得ることは出来た。（2）ジアセチレン誘導体L膜の構造と紫外光照射による重合過程の研究 水槽（pH7.5）にPb2+およびCd2+イオンが存在するそれぞれの場合について，末端にカルボキシル基を持つジアセチレン誘導体（以下DA）L膜のEIRスペクトルの表面圧依存性を詳しく解析した。その結果，カルボキシル基のCOO-逆対称伸縮振動バンド（νas(COO)）がPb2+イオン共存下では1493cm-1に観測されるのに対してCd2+イオン共存下では1528cm-1に観測されL膜と金属イオンとの相互作用様式に大きな相違のあること，表面圧20mN/mでの光重合反応はPb2+イオン共存下でのみ進行することが分かった。また，光照射開始後10分までは分子軸の配向には全く変化がないが1493cm-1のνas(COO)バンドの強度が速やかに減少し，10分以後に不規則構造への転移を含む配向変化が起こることが明らかになり，L膜の光反応に伴う構造緩和にいての重要な知見を得ることが出来た。