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Scattering angle dependence has been experimentally examined for inelasticity effect on the intramolecular interference term observed from the time-of-flight neutron diffraction method. Internuclea...

Experimental evidence has been obtained for the structure-spectra relationship of hydrogen bonds in aqueous solutions. Intramolecular O-D distance, rOD, has been determined by the least-squares fitting analysis of the neutron interference term in the high-Q region observed for pure D2O and concentrated aqueous solutions. The average O-D stretching frequency, νOD, has been obtained from the position of the center of gravity of the observed ATR-IR O-D stretching band. The linear relationship between rOD and νOD has been confirmed in the liquid state. The slope of dνOD/drOD is evaluated to be -21 000 ± 1000 cm-1 A-1.

Neutron diffraction measurements on 6Li/7Li isotopically substituted 10 and 33 mol % *LiTFSA (lithium bis(trifluoromethylsulfonyl)amide)-AN-d3 (acetonitrile-d3) and 10 and 33 mol % *LiTFSA-DMF-d7(N,N-dimethylformamide-d7) solutions have been carried out in order to obtain structural insights on the first solvation shell of Li+ in highly concentrated organic solutions. Structural parameters concerning the local structure around Li+ have been determined from the least squares fitting analysis of the first-order difference function derived from the difference between carefully normalized scattering cross sections observed for 6Li-enriched and natural abundance solutions. In 10 mol % LiTFSA-AN-d3 solution, 3.25 ± 0.04 AN molecules are coordinated to Li+ with a intermolecular Li+···N(AN) distance of 2.051 ± 0.007 A. It has been revealed that 1.67 ± 0.07 AN molecules and 2.00 ± 0.01 TFSA- are involved in the first solvation shell of Li+ in the 33 mol % LiTFSA-AN solution. The nearest neighbor Li+···NAN and Li+···OTFSA- distances are obtained to be r(Li+···N) = 2.09 ± 0.01 A and r(Li+···O) = 1.88 ± 0.01 A, respectively. The first solvation shell of Li+ in the 10 mol % LiTFSA-DMF-d7 solutions contains 3.4 ± 0.1 DMF molecules with an intermolecular Li+···ODMF distance of 1.95 ± 0.02 A. In highly concentrated 33 mol % LiTFSA-DMF-d7 solutions, there are 1.3 ± 0.2 DMF molecules and 3.2 ± 0.2 TFSA- in the first solvation shell of Li+ with intermolecular distances of r(Li+···ODMF) = 1.90 ± 0.02 A and r(Li+···OTFSA-) = 2.01 ± 0.01 A, respectively. The Li+···TFSA- contact ion pair stably exists in highly concentrated 33 mol % LiTFSA-AN and -DMF solutions.

Neutron diffraction measurements have been carried out on 10 mol % LiTFSA (TFSA: bis(trifluoromethylsulfonil)amide) solutions in methanol- d4 and 2-propanol- d8 to obtain information on the solvation structure of Li+. The detailed coordination structure of solvent molecules within the first solvation shell of Li+ was determined through the least-squares fitting analysis of the difference function between normalized scattering cross sections observed for 6Li/7Li isotopically substituted sample solutions. The nearest-neighbor Li+···O distance and coordination number determined for the 10 mol % LiTFSA-methanol- d4 solution are rLiO = 1.98 ± 0.02 A and nLiO = 3.8 ± 0.6, respectively. In the 2-propanol- d8 solution, it has been revealed that 2-propanol- d8 molecules within the first solvation shell of Li+ take at least two different coordination geometries with the intermolecular nearest-neighbor Li+···O distance of rLiO = 1.93 ± 0.04 A. The Li+···O coordination number, nLiO = 3.3 ± 0.3, is determined. Ion-pair formation in the LiTFSA-methanol and LiTFSA-2-propanol solutions has been investigated by the attenuated total reflection infrared spectroscopic method. Mole fractions of free, Li+-bound, and aggregated TFSA- are derived from the peak deconvolution analysis of vibrational bands observed for TFSA-.

Experimental evidence has been presented on the difference in intermolecular ion-water distances obtained from X-ray and neutron diffraction methods. Simultaneous least squares fitting procedures w...

A new determination is presented for the intermolecular partial pair correlation functions of liquid water at ambient temperature. Time-of-flight (TOF) neutron diffraction measurements with excelle...

Neutron diffraction measurements have been carried out for 6Li/7Li isotopically substituted aqueous 1.0 mol % (0.5 mol/kg) LiCl and 1.1 mol % (0.56 mol/kg) LiClO4 solutions in D2O to obtain structural insight concerning hydration structure of Li+ in more dilute electrolyte solutions. The first-order difference function, ΔLi(Q), was analyzed by means of the least squares fitting procedure to obtain short-range structural parameters around the Li+. It was revealed that the nearest neighbor Li+···O(D2O) distance, rLiO, and the coordination number, nLiO, for the aqueous 1.0 mol % LiCl solution are 2.01 ± 0.02 A and 5.9 ± 0.1, respectively. The values, rLiO = 1.97 ± 0.02 A and nLiO = 6.1 ± 0.1, are obtained for aqueous 1.1 mol % LiClO4 solution. These results indicate that the hydration number of Li+ in a dilute solution is close to 6, which is much larger than 4, which has long been believed. A possible explanation is that the hydration number of Li+ varies with the solute concentration.

Isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for concentrated LiTFSA-EC solutions to obtain structural insight on solvated Li+ as well as the structure of contact ion pair, Li+···TFSA–, formed in highly concentrated EC solutions. Symmetrical stretching vibrational mode of solvated Li+ and solvated Li+···TFSA– ion pair were observed at ν = 168–177 and 202–224 cm–1, respectively. Detailed structural properties of solvated Li+ and Li+···TFSA– contact ion pair were derived from the least-squares fitting analysis of first-order difference function, ΔLi(Q), between neutron scattering cross sections observed for 6Li/7Li isotopically substituted 10 and 25 mol % *LiTFSA-ECd4 solutions. It has been revealed that Li+ in the 10 mol % LiTFSA solution is fully solvated by ca. 4 EC molecules. The nearest neighbor Li+···O(EC) distance and Li+···O(EC)═C(EC) bond angle are determined to be 1.90 ± 0.01 A and 141 ± 1°, respectively. In highly concentrated 25 mol % LiTFSA-EC ...

Neutron diffraction measurements have been carried out on 10 mol % LiTFSA (TFSA: bis(trifluoromethylsulfonil)amide) solutions in methanol- d

Low-frequency isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for (6)Li/(7)Li and H/D isotopically substituted *LiCl- and *LiClO4-tetrahydrofuran (*THF) solutions in order to obtain microscopic insight into solvated Li(+), Li(+)···Cl(-) and Li(+)···ClO4(-) contact ion pairs formed in concentrated THF solutions. Symmetrical stretching vibrational mode of solvated Li(+) in LiCl and LiClO4 solutions was observed at ν = 181-184 and 140 cm(-1), respectively. The stretching vibrational mode of Li(+)···Cl(-) and Li(+)···ClO4(-) solvated contact ion pairs formed in 4 mol % (6)LiCl-THF-h8 and (7)LiCl-THF-h8 solutions was found at ν = 469 and 435 cm(-1), respectively. Detailed structural properties of solvated Li(+) and the contact ion pairs were derived from the least-squares fitting analyses of the first-order difference function, ΔLi(Q), obtained from neutron diffraction measurements on (6)Li/(7)Li isotopically substituted THF-d8 solutions. It has been revealed that Li(+) takes 4-fold coordination in the average local structure of Li(+)X(-)(THF)3, X = Cl and ClO4. The nearest neighbor Li(+)···O(THF) distance was determined to be 2.21 ± 0.01 Å and 2.07 ± 0.01 Å for 4 mol % *LiCl- and 10 mol % *LiClO4-THF-d8 solutions, respectively. The Li(+)···anion distances for Li(+)···Cl(-) and Li(+)···O(ClO4(-)) contact ion pairs were determined to be 2.4 ± 0.1 Å and 2.19 ± 0.01 Å, respectively. The nearest neighbor Li(+)···THF interaction is significantly modified by the anion in the first solvation shell.

Neutron diffraction measurements have been carried out at 25 °C for 9.6 mol% ⁎LiPF6-deutrerated dimethyl carbonate (DMC-d6) solutions in which the isotopic ratio of 6Li/7Li was changed. Local structure of Li+ in the solution was derived from the least squares fitting analysis of observed difference function, ΔLi(Q). It was revealed that Li+ is surrounded by ca. 3 DMC molecules and ca. 1 PF6− with intermolecular distances of r(Li+⋯O(DMC)) = 2.08 ± 0.02 A and r(Li+⋯F(PF6−)) = 2.03 ± 0.06 A, respectively. Raman experimental study and DFT calculations agree well with neutron structure analysis.

Isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for concentrated LiTFSA-EC solutions to obtain structural insight on solvated Li

Neutron diffraction measurements were carried out at 25 °C for aqueous LiNO3 heavy water solutions, (*LiNO3) x (D2O)1−x where x = 0.1, 0.05 and 0.01, in which the 6Li/7Li isotopic ratios were varied. Structural information on intermolecular nearest neighbor Li+···D2O interactions in the extensive concentration range was derived from the first-order difference function, ∆Li(Q), obtained from the difference in scattering cross sections between 6Li- and 7Li-enriched sample solutions. The nearest neighbor Li+···O distance and coordination number for sample solution with x = 0.1 were determined to be r LiO = 1.969 (8) A and n LiO = 4.12 (6), respectively, corresponding to the four-coordinated Li+ ion in the solution. On the other hand, those obtained for the solution with x = 0.01 are r LiO = 2.00 (2) A and n LiO = 6.0 (2), respectively, indicating that hexaaqua Li+ is dominant in the dilute solution. These results clearly indicate that a concentration dependence of the hydration number of Li+ occurs in the aqueous solutions.

High-energy X-ray diffraction measurements were carried out at 26 °C for aqueous 1.0, 2.0 and 2.05 mol% disodium adenosine 5′-triphosphate (ATP) and 2.0 and 2.05 mol% disodium adenosine 5′-diphosphate (ADP) solutions in order to obtain direct experimental information on the intramolecular conformations of ATP and ADP molecules in aqueous solutions. Observed interference terms were analyzed in terms of the intramolecular geometry of the ATP and ADP molecules. Dihedral angles between adenine and the ribose group (t1), ribose-ring and methylene group of ribose (t2), and the methylene group of ribose and triphosphate (or diphosphate) group (t3), were determined through the least-squares fitting procedure of the observed interference term.

Neutron diffraction with 14N/15N, 35Cl/37Cl, and 6Li/7Li isotopic substitution methods have been applied to aqueous 10 mol % urea solutions involving 5 mol % NaCl and 10 mol % LiCl, in order to obt...

Neutron diffraction measurements were carried out at 25 °C for aqueous 10 mol% pyridine heavy water solutions, (C5∗H5∗N)0.1(D2O)0.9, in which the isotopic compositions 14N/15N and HPy/DPy (HPy: Pyridine hydrogen atom), were changed. The hydration structure of pyridine molecule was derived from the least squares fitting analysis of observed intermolecular first-order difference functions, ΔNinter(Q) and ΔHinter(Q). It was revealed that a pyridine molecule forms hydrogen bonds of the N⋯DW1 OW DW2 type (DW1, DW2: deuterium atoms in D2O, OW: oxygen atom in D2O) with 2.5(2) water molecules (rN⋯DW1 = 1.95(1) A, ∠N⋯DW1 OW = 174(11)°). The average number of water molecules around the hydrogen atom of the pyridine molecule was determined to be 1.2(1) with the average intermolecular HPy⋯D2O distance of 2.82(1) A.

Hydration behavior of a rare sugar, D-psicose, was investigated based on measurements of the dielectric relaxation and the water activity in its aqueous solutions. Dielectric relaxation spectra in the frequency domain were obtained from time domain reflectometry. The dielectric relaxation time was then determined by fitting the spectra to a Cole-Cole type equation and used to evaluate the average hydration number representing the average number of water molecules forming a complex with a sugar molecule at infinite dilution. The concentration dependence of the dielectric relaxation time in aqueous solutions of all examined sugars generated a single master cur ve. The average hydration number of psicose was found to be identical with that of fructose. Only slight differences were noticeable among the concentration dependences of the water activity of monosaccharides. The equilibrium constant of hydration of sugar was calculated by considering material balances in an aqueous solution of sugar and using experimentally obtained values of the average hydration number and the water activity. The equilibrium constant values increased in the order of glucose < fructose � psicose < trehalose < sucrose < maltose. The present results suggest that both fructose and psicose interact with water in a similar manner.

X-ray diffraction measurements for the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF 4 ], mixed with CO 2 were carried out at high pressures using our developed polymer cell. The intermolecular distribution functions obtained for IBMIMI[BF 4 ]-CO 2 mixtures showed that C0 2 molecules are preferentially solvated to the [BF 4] - anion. The similar preferential solvation was previously observed in analogous 1-btuyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF 6 ], with a different anion, which is in harmony with the present results in [BMIM][BF 4 ]-CO 2 .

Neutron diffraction measurements were carried out on 14N/15N and H/D isotopically substituted aqueous 25 mol % urea (xurea = 0.25) solutions in order to obtain direct experimental information on th...

Neutron diffraction measurements were carried out on aqueous alkaline 2 mol % glycine heavy water solutions absorbing CO2. 14N/15N isotopic substitution was applied to obtain information on the mol...

Polarized Raman spectra for concentrated aqueous KX solutions (X: Cl, Br, NO3, and SCN) were measured in the frequency range of 30 ≤−1 in order to find the totally symmetric stretching vibrational ...

X-ray diffraction measurements on aqueous 2.5 mol % DL-, L-, and D-alanine solutions in D2O were carried out at 26±2 °C in order to obtain information concerning the difference in the hydrogen-bond...

High-energy X-ray diffraction, neutron diffraction and extended X-ray absorption fine structure experiments have been carried out for (AgI) x (As 2 Se 3 ) 1− x glasses. The addition of a large amount of AgI does not significantly affect the short-range ordering of the host network matrix, that is, As(Se 1/2 ) 3 pyramidal units remain essentially intact on introducing AgI. The interatomic distance of Ag–I pairs is similar to the case of crystalline AgI. However, the coordination number of Ag–I pairs in the present glasses seems to be somewhat smaller than that in the crystalline AgI, suggesting a heavy distortion of tetrahedral coordinates of AgI units or structural disorder of the I–I sub cages in the glass state.

Time-of-Flight (TOF) neutron diffraction measurements with the 6Li/7Li isotopic substitution technique were carried out for aqueous 18 mol% lithium alaninate solutions in D2O in order to obtain structural information on the interaction between Li+ and the amino acid molecule in the concentrated aqueous solution. The first-order difference function, ΔLi(Q), was obtained from the difference between scattering cross sections observed for solutions involving dl -CH3CH(ND2)COO6Li and dl -CH3CH(ND2)COO7Li. The distribution function around Li+, GLi(r), exhibits well resolved first and second peaks that are tentatively attributable to the nearest neighbor Li+ ⋯ O and Li+ ⋯ D interactions. However, the coordination number, nLiD, estimated from the area under the second peak is found to be much larger than the value, 2nLiO, evaluated from the first peak of the present GLi(r). This implies that the nearest neighbor Li+ ⋯ alaninate ion interaction may contribute to the second peak. Structural parameters concerning the first coordination shell of the Li+ has been determined through the least squares fitting analysis of the observed ΔLi(Q). It has been revealed that the Li+ is surrounded by 2.4(1) D2O molecules and 2.3(2) alaninate ions with interatomic distances of r(Li+ ⋯ OD2O) = 1.97(1) A, r(Li+ ⋯ DD2O) = 2.62(1) A and r(Li+ ⋯ Oalaninate) = 2.38(1) A, respectively.

Neutron diffraction measurements were carried out on 14N/15N isotopically substituted aqueous 5 mol % sodium L-hydrogenglutamate solutions in D2O in order to obtain direct information concerning th...

Neutron diffraction measurements on 35 Cl /37 Cl isotopically substituted anion exchange resins were carried out in order to obtain direct information on the local structure around the chloride ion absorbed in the resin. Structural parameters concerning the first nearest-neighbor interaction of chloride ions were determined through a least-squares fitting procedure of the observed first-order difference function, Δ Cl (Q). It has been revealed that the chloride ion is neighboring an ion exchange group (-CH 2 (CH 3 ) 3 N + ) with a Cl - ···N distance of 3.10(3) A, and simultaneously bonded with 2.4(1) D 2 O molecules with a C1 - ···D distance of 2.25(2) A. The second and third nearest water molecules around Cl - have also been observed. These results indicate that the direct ionic interaction between Cl - and -CH 2 (CH 3 ) 3 N + drastically reduces the number of first-neighbor water molecules around Cl - but enhances the long-distance structuring of the remaining water molecules in the environment surrounded by a hydrophobic polymer matrix.

Dielectric spectra of binary mixtures of propanediamine (PDA) and propanediol (PDO) are measured by TDR (time domain reflectometry). The KWW (Kohlrausch–Williams–Watts) function is used to obtain relaxation parameters. The observed relaxation time has a maximum at around 0.7 mole fraction of PDO. The concentration dependence of the relaxation time suggests that the intermolecular interaction between PDA and PDO is stronger than that of pure amines and of pure alcohols.

X-ray diffraction and diffuse reflection IR spectroscopic measurements have been carried out on amorphous NaCl–glucose mixtures, a-(NaCl)x(glucose)1−x, with x = 0, 0.05, 0.1 and 0.15, in order to obtain structural information on the intermolecular hydrogen-bonded interaction between glucose molecules affected by the presence of NaCl. The difference distribution function Δginter(r) was derived from the Fourier transform of the difference intermolecular interference term Δiinter(Q) between X-ray intermolecular interference terms observed from amorphous NaCl-glucose and pure glucose samples. A negative peak appears at r ≈ 2.5 A in the Δginter(r) observed for the 10 mol% NaCl sample, while, the Δginter(r) for the 15 mol% NaCl sample does not show pronounced negative peak. On the other hand, the IR spectra for the O–H stretching region (2300 ⩽ ν ⩽ 3800 cm−1) indicate that hydrogen bonds between glucose molecules are significantly collapsed in the samples containing 5–15 mol% NaCl. These results imply that the contribution from the Na+⋯Cl− contact ion pair is dominated in the 15 mol% NaCl sample.

Time-of-flight neutron diffraction measurements were carried out for 6Li/7Li isotopically substituted 10 mol % LiPF6-propylene carbonate-d6 (PC-d6) solutions, in order to obtain structural information on the first solvation shell of Li+. Structural parameters concerning the nearest neighbor Li+...PC and Li+...PF6- interactions were determined through least-squares fitting analysis of the observed difference function, DeltaLi(Q). It has been revealed that the first solvation shell of Li+ consists in average of 4.5(1) PC molecules with an intermolecular Li+...O(PC) distance of 2.04(1) A. The angle Li+...O=C bond angle has been determined to be 138(2) degrees.

Neutron diffraction measurements were carried out at 25°C on aqueous 15 mol % urea heavy water solutions, [(ND 2 ) 2 *C=O] 0.15 (D 2 O) 0.85 , in which the 12 C/ 13 C isotopic composition of the carbonyl-carbon atom was changed. The hydration structure around the carbonyl-carbon atom was derived from the least-squares fitting analysis of the observed first-order difference function, Δ C (Q). From the analysis, 4.3(3) water molecules are hydrogen-bonded to the carbonyl-oxygen atom with the intermolecular C···D W1 (D W1 : water deuterium atom) distance of 2.46(3) A. The average angle, LC...D W1 -O W (O W : water oxygen atom), was determined to be 124(5)°.

Neutron diffraction measurements were carried out for anion and cation exchange resins (AER and CER, respectively) absorbing H/D isotopically substituted water molecules in order to obtain structural information on the hydrogen-bonded network among water molecules within the resins. Partial structure factors, a HH (Q), a XH (Q), and a XX (Q) (X: atoms involved in the sample except for water-hydrogen atom), for AER and CER samples were respectively deduced from combined analyses of intermolecular interference terms observed for resins containing D 2 O (99.8% D), 0 H 2 O (35.9% D), and 0-2 H 2 O (67.9% D). The nearest neighbor distances, r(O-H) = 1.95(3) A and r(H···H) = 2.40(3) A, determined for the AER sample agree well with those reported for pure liquid water. On the other hand, considerably shorter intermolecular distances, r(O···H) = 1.78(3) A and r(H···H) = 2.28(3) A, were found for the CER sample, implying that the hydrogen-bonded network among water molecules in CER would be strongly affected by a highly acidic environment.

Neutron diffraction measurements have been carried out at 25 °C for aqueous 18 mol % lithium alaninate heavy water solutions, [C*H3C*H(*ND2)COO*Li]0.18(D2O)0.82, in which the isotopic compositions ...

Time-of-flight neutron diffraction and infrared (IR) double difference spectral measurements have been carried out on aqueous 4 mol% lithium benzoate solutions. The neutron diffraction with isotopic substitution technique has been applied to both lithium and benzyl-hydrogen atoms within the benzoate ion in order to obtain information on the hydration structure around both the lithium ion and the benzyl-hydrogen atom within the benzoate ion. The observed first-order difference functions, ΔLi(Q) and ΔHinter(Q), were analyzed by the least squares fitting procedure. The number of water molecules within the first hydration shell of the Li+ was determined to be 5.3(1) with the Li+···O and Li+···D distances of 1.95(1) and 2.58(1) A, respectively. A well-defined second hydration shell involving 6.0(1) water molecules, has been found and characterized by the Li+···O and Li+···D distances of 4.12(1) and 4.73(1) A, respectively. The first hydration shell of the benzyl-hydrogen atoms (Hb) within the benzoate ion was found to consist of 1.0(1) water molecule with the average Hb···D2O intermolecular distance of 2.78(1) A. Results of the IR double difference spectra exhibited that the number of water molecules within the first hydration shell of Li+ is 5.7(1), in reasonable agreement with that obtained from the neutron diffraction data. The hydration number of the carboxyl group within the benzoate ion was determined to be 4.9(1) from the IR difference spectra.

Time-of-Flight (TOF) neutron diffraction measurements were carried out for 12 mol% *HCOO7Li solutions in D2O. The H/D isotopic substitution technique was applied to the formyl-hydrogen atom of the ...

Time-of-Flight (TOF) and steady state reactor neutron diffraction measurements have been carried out for aqueous 2.5 mol% DL- and L-alanine solutions in order to invest gate the differences in intermolecular hydrogen-bonded structure between solutions involving amino acid molecules with different optical activities. The observed difference functions, Δi(Q) and Δi i n t e r (Q), between observed scattering cross sections for DL- and L-alanine solutions with a D content of 96.1% exhibit the first peak located at Q = 2A - 1 followed by oscillatory features extending up to the higher-Q region. The difference distribution function, Δg(r), obtained from the Fourier transform of Δi(Q), clearly indicates negative peaks at r = 2 and 2.5 A and a positive one at r = 3.5 A. Partial structure factors, a H H (Q), a X H (Q), and a X X (Q) (X: O, N, C, H M , and H M ' where H M and H M ' denote methyl and methine hydrogen atoms within the alanine molecule, respectively) for 2.5 mol% DL-alanine solutions are successfully determined from combined analyses of intermolecular interference terms observed for solutions with 96.1, 66.0, and 35.9% exchangeable deuterium content. The nearest neighbor O...H e x and H e x ...H e x (H e x : exchangeable hydrogen atom) distances are determined from the least squares fit of the observed partial structure factors, 1.90(1) and 2.48(1) A, respectively. These values correspond to the positions of negative peaks observed in the present Δg(r) function. The least squares fitting analysis of the observed Ai(Q) revealed that the difference in the coordination number of the nearest neighbor O...H e x and H e x ...H e x interactions between the DL- and L-alanine solutions are -0.031(5) and --0.072(5), respectively. It is concluded that the intermolecular hydrogen bonds among solvent water molecules in the DL-alanine solution are ca. 2% weaker than those in the L-alanine solution.

Low-frequency Raman scattering of water–ethylene glycol oligomer (EGO) binary mixtures have been carried out. Reduced spectra of mixtures were decomposed into a linear combination of pure water and neat EGO spectra. The superposed spectra systematically deviate from the measured spectra of mixtures below 80 cm−1. Integrated intensity of the difference between obtained spectrum and superposed spectrum, Δχ″, depends on both the concentration and the unit numbers of EGO. Small Δχ″ and nonlinear concentration dependence of the coefficients of linear combination are related to the cooperative motions of EGO and water molecules.

Low-frequency Raman scattering spectra have been measured for tert-butyl alcohol (TBA)–water and tetrahydrofuran (THF)–water binary mixtures as a function of concentration. We confirmed the isosbestic point in the reduced Raman spectra χ″(ν) of the TBA–water and THF–water mixtures. The χ″(ν) spectra could be decomposed into a linear combination of the neat TBA spectrum and the pure water spectrum in the frequency range from 80 to 400 cm−1. On the other hand, below 80 cm−1, the χ″(ν) spectra could not be decomposed into a linear combination. The superposed spectra deviated systematically from the experimental spectra as a function of solute concentration. This result indicated that cooperative dynamics was present in TBA–water and THF–water mixtures although the intermolecular vibrations showed independent character.

High frequency Raman scattering spectra of (KH2PO4)1−x(KD2PO4)x have been reproduced by a simple addition of KH2PO4 (KDP) and KD2PO4 (DKDP) spectra. Through this procedure we can separate the hydrogen (deuterium) modes from the PO4 internal vibration modes. The frequency ratio of the hydrogen modes to the deuterium modes is 1.37 both in the paraelectric phase and ferroelectric phase.

Depolarized low-frequency(LF) Raman spectra of AX (ALi, Na, K, Rb, Cs; X  Cl, Br, I) aqueous solutions have been investigated over a wide concentration range. The reduced spectra were analyzed with one relaxation function based on the multiple random telegraph(MRT) model and two damped harmonic oscillators. One of the fitting parameter, Kubo number α0, corresponding to the modulation speed in the MRT model is found to be a good indicator of the structure making and breaking effects for water by ACl and ABr.

Low-wavenumber Raman scattering spectra of aqueous NaI solutions were measured with 488.0 and 514.5 nm excitation. The enhancement of the spectral intensity caused by I− ion does not depend on the excitation wavelength. We can apply the phenomenological analysis to the low-wavenumber Raman spectra of alkali metal halide aqueous solutions even when the ‘pre-resonance effect’ of proton transfer changes the mode intensity. Copyright © 2002 John Wiley & Sons, Ltd.

Rayleigh–Brillouin scattering was performed for water and alcohol (methanol, ethanol, 1-propanol and 2-propanol) binary mixtures. The Landau–Placzek ratio depends on both concentrations and molecular weights, and qualitatively corresponds to the ultrasonic absorption. Microscopic concentration fluctuation mainly affects the Landau–Placzek ratio of water–alcohol mixtures.

The salt effect on the phase transition of N-isopropylacrylamide (NIPA) gel was studied. The swelling behavior of the NIPA gel strongly depends on the salt concentration and is well described as a function of the chemical potential difference of water molecules in solution from that at the transition. From the analysis of the OH stretching, Raman spectra in water and in various aqueous solutions in terms of collective proton motions reveals that the presence of salts tends to disrupt or distort the water molecules in hydrophobic hydration shell around the NIPA gel. This leads to inducing the growth of the cluster shell around the salts, which leads to gel collapse. The volume phase transitions due to the different types of perturbation (temperature, salt) are induced by the same mechanism, hydrophobic hydration and dehydration, and therefore can be described in a unified manner in terms of the chemical potential and the collective proton motions of water molecules.

Low-frequency Raman spectra of ethanol–water mixtures as a function of concentration are measured. We reconfirm the isosbectic point at 130 cm−1 in the χ′′(ν) spectra [1] . The χ′′(ν) spectra of the mixtures can be decomposed into the linear combination of pure water and neat ethanol in the frequency range from 40 to 250 cm−1. Below 40 cm−1, the spectra cannot be decomposed into the linear combination and systematic deviations are found. The results indicate that the microscopic aggregation of water and ethanol molecules depends on the mixing ratio.

Depolarized low-frequency Raman spectra of H 2 O , D 2 O , H 2 18 O , and D 2 18 O are measured from 266 to 350 K. The reduced Raman spectra below 250 cm −1 are reproduced by a superposition of one relaxation mode and two damped harmonic oscillators. The multiple random telegraph model, which takes into account the inertia and memory effects is applied to analyze the central relaxation component. The 180 cm −1 mode corresponds to vibration of the oxygen atom. The hydrogen isotopes affect the relaxation time causing its variation. The relaxation time is considered to correspond to the duration of fluctuation of the local structure in liquid water. The intensity of the 50 cm −1 mode decreases with increasing temperature and finally vanishes above about 300–310 K. The 50 cm −1 mode can be distinguished from the relaxation mode when the relaxation time is more than five times longer than the period of the 50 cm −1 vibration mode.