Vibrational modes of hydrogens in the proton ordered phase XI of ice: Raman spectra above 400 cm(-1)

Polarized Raman spectra of the proton ordered phase of ice Ih, i.e., ice XI, were measured above 400 cm(-1) in the range of librational, bending, and stretching vibrations. Vibrational modes in ice XI, of which symmetry is C(2v) (12)(Cmc2(1)), were discussed from the group theoretical point of view. In the librational mode spectra below 1200 cm(-1), several new peaks and clear polarization dependencies were observed. Assignments of the librational modes agree reasonably well with the recent MD calculations by Iwano et al. (J. Phys. Soc. Jpn. 79, 063601 (2010)). In contrast, the spectra for bands above 1200 cm(-1) show no distinct polarization dependencies and the spectra resemble those in ice Ih. In ice XI, however, fine structure composed of several weak peaks appear on the broad bending and the combination band. No direct evidence of the LO-TO splitting of the ν(3) anti-symmetric stretching mode was obtained. It is contrary to the case of the translational modes Abe and Shigenari (J. Chem. Phys. 134, 104506 (2011)). Present results suggest that the influence of the proton ordering in ice XI is weaker than the effect of inter- and intra-molecular couplings in the stretching vibrations of ice Ih.     

Raman spectroscopy of uranyl rare earth carbonate kamotoite-(Y)

Raman spectroscopy at 298 and 77K has been used to study the mineral kamotoite-(Y), a uranyl rare earth carbonate mineral of formula Y(2)(UO(2))(4)(CO(3))(3)(OH)(8).10-11H(2)O. The mineral is characterised by two Raman bands at 1130.9 and 1124.6 cm(-1) assigned to the nu(1) symmetric stretching mode of the (CO(3))(2-) units, while those at 1170.4 and 862.3 cm(-1) (77K) to the deltaU-OH bending vibrations. The assignment of the two bands at 814.7 and 809.6 cm(-1) is difficult because of the potential overlap between the symmetric stretching modes of the (UO(2))(2+) units and the nu(2) bending modes of the (CO(3))(2-) units. Only a single band is observed in the 77K spectrum at 811.6 cm(-1). One possible assignment is that the band at 814.7 cm(-1) is attributable to the nu(1) symmetric stretching mode of the (UO(2))(2+) units and the second band at 809.6 cm(-1) is due to the nu(2) bending modes of the (CO(3))(2-) units. Bands observed at 584 and 547.3 cm(-1) are attributed to water librational modes. An intense band at 417.7 cm(-1) resolved into two components at 422.0 and 416.6 cm(-1) in the 77K spectrum is assigned to an Y(2)O(2) stretching vibration. Bands at 336.3, 286.4 and 231.6 cm(-1) are assigned to the nu(2) (UO(2))(2+) bending modes. U-O bond lengths in uranyl are calculated from the wavenumbers of the uranyl symmetric stretching vibrations. The presence of symmetrically distinct uranyl and carbonate units in the crystal structure of kamotoite-(Y) is assumed. Hydrogen-bonding network related to the presence of water molecules and hydroxyls is shortly discussed.     

Effects of torsion on O-H stretch overtone spectra and direct overtone photolysis of methyl hydroperoxide

We use laser photoacoustic spectroscopy to obtain overtone spectra at three through six quanta of O-H stretch excitation (3nu(OH)-6nu(OH)) for methyl hydroperoxide (MeOOH). Extending the spectral regions beyond our previous work reveals new features that can be attributed to transitions involving torsion about the O-O bond. Experimental spectral profiles (3nu(OH)-6nu(OH)) and cross sections (3nu(OH)-5nu(OH)) at room temperature show a good agreement with the simulated spectra that we obtain from ab initio calculations employing a vibration-torsion model at 298 K. A Birge-Sponer analysis yields experimental values for the O-H stretch frequency (omega=3773+/-15 cm(-1)) and anharmonicity (omegax=94+/-3 cm(-1)). We also detect OH radicals by laser-induced fluorescence and present photodissociation action spectra of MeOOH in the regions of 4nu(OH) and 5nu(OH). While the spectral profile at 5nu(OH) mimics the photoacoustic spectrum, the peak intensity for transitions to torsionally excited states is relatively more intense in the action spectrum at 4nu(OH), reflecting the fact that the 4nu(OH) excitation energy is below the literature dissociation energy (D0=42.6+/-1 kcal mol(-1)) so that features in the action spectrum come from thermally populated excited states. Finally, we use our calculations to assign contributions to individual peaks in the room-temperature spectra and relate our findings to a recent dynamics study in the literature.     

Low-frequency modes of the benzoic acid dimer in chloroform observed by the optical Kerr effect

The low frequency Raman spectral density associated with the intermolecular hydrogen-bonding interaction of benzoic acid in chloroform was investigated through the ultrafast optically-heterodyne-detected optical Kerr effect. The low-frequency solute Raman spectrum was obtained by Fourier transform analysis and subtraction of the solvent spectrum from the solution spectrum. The resulting difference spectrum has a broad band below 150 cm(-1) with a peak at around 80 cm(-1). Previous studies of aromatic liquids suggest that the origin of such a low-frequency band is librational motion, although intermolecular hydrogen-bonding modes in benzoic acid may also contribute. To clarify these contributions to the low-frequency band, methyl benzoate was used to estimate the librational component; its structure is similar to benzoic acid, but it forms no intermolecular hydrogen bonds. Both librational and intermolecular modes were found to contribute to the low-frequency Raman spectrum of the dimer and thus can be separated. These experimental results were compared with the results of density functional theory calculations. In addition, the effect of deuteration on the Raman spectrum was also investigated.     

Dimensional effects on the LO-TO splitting in CF4: first-principles and infrared absorption studies

The development of longitudinal optical-transverse optical (LO-TO) modes in CF(4) has been studied experimentally and theoretically as a function of dimensionality. Infrared absorption experiments for CF(4) adsorbed on single-walled carbon nanotubes indicate a lack of LO-TO splitting at low coverage and a gradual appearance of LO-TO modes as the coverage of CF(4) on the nanotubes is increased. We have performed density functional perturbation theory calculations for the vibrational frequencies, IR absorption spectra, and phonon density of states for CF(4) in one, two, and three dimensions. The calculations demonstrate that LO-TO splitting in 1D is qualitatively different from that computed for 2D or the bulk. The magnitude of the splitting in 1D is about one-half that computed for the bulk, and the LO mode is very weakly blue-shifted in 1D. We predict that the phonon density of states changes dramatically as the dimensionality of the crystal is changed. This prediction can be tested experimentally via inelastic neutron scattering. We conclude that LO-TO splitting can be used as a probe to identify 1D states of matter.     

Vibronic spectroscopy of the peroxyacetyl radical in the near IR

The A 2A'<--X 2A" electronic transition of the peroxyacetyl radical (PA) is observed employing NIR/VUV ion enhancement, supersonic jet spectroscopy. Rotational envelope simulations yield a rotational temperature for ground state PA of ca. 55 K. Ab initio calculations of transition energies and vibrational frequencies for the A<--X transition assist in the assignment of the observed spectrum. A number of the vibrational modes of the A state are assigned to observed transitions (the O-O stretch 2(1), the COO bend 5(1), and the CCOO backbone bend 6(1)). The calculations and mass spectra suggest that the ground state of the PA ion is repulsive. An increase in rotational linewidth of the overtone of the O-O stretch (2(1)) is observed and discussed in terms of A state dynamics. The O-O stretch anharmonicity is estimated to be 13.35 cm(-1).     

Vibrational overtone spectroscopy of jet-cooled methanol from 5000 to 14 000 cm(-1)

Spectra of jet-cooled methanol in the overtone and combination region from 5000 to 14 000 cm(-1) have been obtained by means of infrared laser-assisted photofragment spectroscopy. Many of the observed features are assigned to combination bands of the type nnu(1)+nu(6), nnu(1)+nu(8), and nnu(1)+nu(6)+nu(8) (n=1,2,3), where nu(1) is the OH stretch, nu(6) is the OH bend, and nu(8) is the CO stretch. These bands show sharp torsion-rotation structure with features as narrow as 0.1 cm(-1). We also observe CH stretch overtones that are weaker than the OH containing combination bands and lack distinct torsion-rotation structure above v(CH)=2. The extent of observed structure on these bands allows us to place limits on the intramolecular vibrational energy redistribution decay rates in the upper vibrational states. We report a global fit of the observed band centers to a simple expression involving low-order anharmonicity constants.     

Unimolecular processes in CH2OH below the dissociation barrier: O-H stretch overtone excitation and dissociation

The OH-stretch overtone spectroscopy and dynamics of the hydroxymethyl radical, CH(2)OH, are reported in the region of the second and third overtones, which is above the thermochemical threshold to dissociation to H+CH(2)O (D(0)=9600 cm(-1)). The second overtone spectrum at 10 484 cm(-1) is obtained by double resonance IR-UV resonance enhanced multiphoton ionization (REMPI) spectroscopy via the 3p(z) electronic state. It is rotationally resolved with a linewidth of 0.4 cm(-1) and displays properties of local-mode vibration. No dissociation products are observed. The third overtone spectra of CH(2)OH and CD(2)OH are observed at approximately 13 600 cm(-1) by monitoring H-atom photofragments while scanning the excitation laser frequency. No double resonance REMPI spectrum is detected, and no D fragments are produced. The spectra of both isotope analogs can be simulated with a linewidth of 1.3 cm(-1), indicating dissociation via tunneling. By treating the tunneling as one dimensional and using the calculated imaginary frequency, the barrier to dissociation is estimated at about 15 200 cm(-1), in good agreement with theoretical estimations. The Birge-Sponer plot is linear for OH-stretch vibrations 1nu(1)-4nu(1), demonstrating behavior of a one-dimensional Morse oscillator. The anharmonicity parameter derived from the plot is similar to the values obtained for other small OH containing molecules. Isomerization to methoxy does not contribute to the predissociation signal and the mechanism appears to be direct O-H fission via tunneling. CH(2)OH presents a unique example in which the reaction coordinate is excited directly and leads to predissociation via tunneling while preserving the local-mode character of the stretch vibration.     

Resonance Raman intensity analysis of the excited state proton transfer dynamics of 2-nitrophenol in the charge-transfer band absorption

Resonance Raman spectra were obtained for 2-nitrophenol in cyclohexane solution with excitation wavelengths in resonance with the charge-transfer (CT) proton transfer band absorption. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion along more than 15 normal modes: the nominal CCH bend+CC stretch nu(12) (1326 cm(-1)), the nominal CCC bend nu(23) (564 cm(-1)), the nominal CO stretch+NO stretch+CC stretch nu(14) (1250 cm(-1)), the nominal CCH bend+CC stretch+COH bend nu(15) (1190 cm(-1)); the nominal CCH bend+CC stretch nu(17) (1134 cm(-1)), the nominal CCC bend+CC stretch nu(22) (669 cm(-1)), the nominal CCN bend nu(27) (290 cm(-1)), the nominal NO(2) bend+CC stretch nu(21) (820 cm(-1)), the nominal CCO bend+CNO bend nu(25) (428 cm(-1)), the nominal CC stretch nu(7) (1590 cm(-1)), the nominal NO stretch nu(8) (1538 cm(-1)), the nominal CCC bend+NO(2) bend nu(20) (870 cm(-1)), the nominal CC stretch nu(6) (1617 cm(-1)), the nominal COH bend+CC stretch nu(11) (1382 cm(-1)), nominal CCH bend+CC stretch nu(9) (1472 cm(-1)). A preliminary resonance Raman intensity analysis was done and the results for 2-nitrophenol were compared to previously reported results for nitrobenzene, p-nitroaniline, and 2-hydroxyacetophenone. The authors briefly discuss the differences and similarities in the CT-band absorption excitation of 2-nitrophenol relative to those of nitrobenzene, p-nitroaniline, and 2-hydroxyacetophenone.     

Spectroscopic characterization of chromite from the Moa-Baracoa Ophiolitic Massif, Cuba

The Cuban chromites with a spinel structure, FeCr2O4 have been studied using optical absorption and EPR spectroscopy. The spectral features in the electronic spectra are used to map the octahedral and tetrahedral co-ordinated cations. Bands due Cr3+ and Fe3+ ions could be distinguished from UV-vis spectrum. Chromite spectrum shows two spin allowed bands at 17,390 and 23,810 cm(-1) due to Cr3+ in octahedral field and they are assigned to 4A2g(F) --> 4T2g(F) and 4A2g(F) --> 4T1g(F) transitions. This is in conformity with the broad resonance of Cr3+ observed from EPR spectrum at g = 1.903 and a weak signal at g = 3.861 confirms Fe3+ impurity in the mineral. Bands of Fe3+ ion in the optical spectrum at 13,700, 18,870 and 28,570 cm(-1) are attributed to 6A1g(S) --> 4T1g(G), 6A1g(S) --> 4T2g(G) and 6A1g(S) --> 4T2g(P) transitions, respectively. Near-IR reflectance spectroscopy has been used effectively to show intense absorption bands caused by electronic spin allowed d-d transitions of Fe2+ in tetrahedral symmetry, in the region 5000-4000 cm(-1). The high frequency region (7500-6500 cm(-1)) is attributed to the overtones of hydroxyl stretching modes. Correlation between Raman spectral features and mineral chemistry are used to interpret the Raman data. The Raman spectrum of chromite shows three bands in the CrO stretching region at 730, 560 and 445 cm(-1). The most intense peak at 730 cm(-1) is identified as symmetric stretching vibrational mode, A1g(nu1) and the other two minor peaks at 560 and 445 cm(-1) are assigned to F2g(nu4) and E(g)(nu2) modes, respectively. Cation substitution in chromite results various changes both in Raman and IR spectra. In the low-wavenumber region of Raman spectrum a significant band at 250 cm(-1) with a component at 218 cm(-1) is attributed F2g(nu3) mode. The minor peaks at 195, 175, 160 cm(-1) might be due to E(g) and F2g symmetries. Broadening of the peak of A1g mode and shifting of the peak to higher wavenumber observed as a result of increasing the proportion of Al3+O6. The presence of water in the mineral shows bands in the IR spectrum at 3550, 3425, 3295, 1630 and 1455 cm(-1). The vibrational spectrum of chromite gives raise to four frequencies at 985, 770, 710 and 650 cm(-1). The first two frequencies nu1 and nu2 are related to the lattice vibrations of octahedral groups. Due to the influence of tetrahedral bivalent cation, vibrational interactions occur between nu3 and nu4 and hence the low frequency bands, nu3 and nu4 correspond to complex vibrations involving both octahedral and tetrahedral cations simultaneously. Cr3+ in Cuban natural chromites has highest CFSE (20,868 cm(-1)) when compared to other oxide minerals.     

Electronic and vibrational spectroscopy and vibrationally mediated photodissociation of V+(OCO)

Electronic spectra of gas-phase V+(OCO) are measured in the near-infrared from 6050 to 7420 cm(-1) and in the visible from 15,500 to 16,560 cm(-1), using photofragment spectroscopy. The near-IR band is complex, with a 107 cm(-1) progression in the metal-ligand stretch. The visible band shows clearly resolved vibrational progressions in the metal-ligand stretch and rock, and in the OCO bend, as observed by Brucat and co-workers. A vibrational hot band gives the metal-ligand stretch frequency in the ground electronic state nu3' = 210 cm(-1). The OCO antisymmetric stretch frequency in the ground electronic state (nu1') is measured by using vibrationally mediated photodissociation. An IR laser vibrationally excites ions to nu1' = 1. Vibrationally excited ions selectively dissociate following absorption of a second, visible photon at the nu1' = 1 <-- nu1' = 1 transition. Rotational structure in the resulting vibrational action spectrum confirms that V+(OCO) is linear and gives nu1' = 2392.0 cm(-1). The OCO antisymmetric stretch frequency in the excited electronic state is nu1' = 2368 cm(-1). Both show a blue shift from the value in free CO2, due to interaction with the metal. Larger blue shifts observed for complexes with fewer ligands agree with trends seen for larger V+(OCO)n clusters.     

Cooperative organic hydrogen bonds: the librational modes of cyclic methanol clusters

Intermolecular hydrogen bond libration modes of isolated cyclic methanol trimers (approximately 613 cm(-1)) and tetramers (695 and 760 cm(-1)) are observed in pulsed jet Fourier transform infrared spectra and found to exhibit sizeable anharmonicity and mode coupling effects, opening the way for a microscopic interpretation of the broad librational bands of alcohols. The correlation of experimental OH stretching and OH libration band intensities provides important constraints for theoretical band strengths, cluster densities, and size assignments.     

Vibrational anharmonicity and vibrational Stark effect of sulfate ions trapped in potassium, rubidium and cesium chromate

Room and low temperature (approximately 100 K) FT-IR and Raman spectra of the sulfate doped K2CrO4, Rb2CrO4 and Cs2CrO4 were recorded. The positions of the nu1, nu3, and nu4 fundamental mode components of the dopant anions were measured. Nine (out of possible ten) second-order stretch-stretch vibrational transitions of the dopant anions were detected. On the basis of these data, the anharmonicity constants and the corresponding harmonic eigenvalues were calculated for several vibrational transitions using second-order perturbation theory expressions. The anharmonicity of the studied second-order transitions of the type nu1 + nu3i increases in the order (SO4/K2CrO4) < (SO4/Rb2CrO4) < (SO4/Cs2CrO4), while for those of the type nu3j + nu3i it basically follows the trend: (SO4/K2CrO4) > (SO4/Rb2CrO4) < (SO4/Cs2CrO4). The measured relative Stark splittings of the nu3 and nu4 mode components of the dopant SO4(2-) anions, as well as the average X13i/3i3j values decrease in the order (SO4/K2CrO4) > (SO4/Rb2CrO4) > (SO4/Cs2CrO4). In all cases, the splitting is larger for nu3 than for nu4 modes, indicating a smaller angular than the bond length distortion. The theory of vibrational Stark effect suggests that the observed frequency shifts of the nu1, nu3 and nu4 mode components may be attributed to the increase of the field strength at the doped anion site going from K2CrO4 to Cs2CrO4. The Stark splitting of these modes, on the other hand, implies that the internal crystalline field vector is almost parallel to the (hypothetical) C2 axis of the slightly distorted dopant tetrahedral anions.     

Contribution of the asymmetric stretch, nu3B1, to the fundamental Raman spectrum of water

The OD-stretching overtone from liquid D2O, 2nu, and the fundamental OD stretch from dilute HDO, both display high-frequency depolarization ratio minima, but the fundamental OD stretch from neat D2O displays a maximum, at the equivalent position. The rhoL minima arises from the decreased depolarization ratio produced by the absence of B1 modes. The fundamentals of HDO are of A species, and the 2nu overtone of D2O only involves A1 species, e.g., 2nu3B1 has A1 species via B1 x B1 = A1. A and A1 modes display small rhoL values which produce minima in rhoL near 2665 cm(-1) for HDO, and near 5250 cm(-1) for the D2O overtone. These minima give way to a depolarization ratio maximum when the depolarized, rhoL = 34, nu3B1 fundamental, makes its appearance in D2O at 2650 cm(-1). Fundamental and overtone depolarization ratios were used to determine the nu3B1 contribution to the depolarization ratio of the fundamental OD stretch; a value of approximately 28% resulted at 2655 cm(-1). Liquid H2O displays completely analogous features; a value of approximately 20% resulted for it at 3660 cm(-1). Nonhydrogen-bonded nu3B1, and more strongly hydrogen-bonded nu3B1, modes are also indicated for D2O and H2O. A rigorous test of the current results can be accomplished by measuring the depolarization ratio of the extraordinarily weak second Raman overtone, 3nu, recently detected for D2O.     

Observation of the Low‐Frequency Spectrum of the Water Dimer as a Sensitive Test of the Water Dimer Potential and Dipole Moment Surfaces

Using the helium nanodroplet isolation setup at the ultrabright free‐electron laser source FELIX in Nijmegen (BoHeNDI@FELIX), the intermolecular modes of water dimer in the frequency region from 70 to 550 cm^?1 were recorded. Observed bands were assigned to donor torsion, acceptor wag, acceptor twist, intermolecular stretch, donor torsion overtone, and in‐plane and out‐of‐plane librational modes. This experimental data set provides a sensitive test for state‐of‐the‐art water potentials and dipole moment surfaces. Theoretical calculations of the IR spectrum are presented using high‐level quantum and approximate quasiclassical molecular dynamics approaches. These calculations use the full‐dimensional ab initio WHHB potential and dipole moment surfaces. Based on the experimental data, a considerable increase of the acceptor switch and a bifurcation tunneling splitting in the librational mode is deduced, which is a consequence of the effective decrease in the tunneling barrier.     

Solid state effects in the IR spectrum of octahydridosilasesquioxane

Infrared spectrum of Octahydridosilasesquioxane, in the solid state, is reported and analyzed to show the presence of significant solid state effects. This is in marked contrast with the reported Raman spectroscopic studies of this compound in the solid state where no evidence for such a proliferation of these effects were found. It is found that the normal modes with radial motion of the atoms in their normal coordinate are distinguishable from other vibrations by the distinct correlations between the band intensity and the solid state splitting observed in the IR spectrum. This new insight suggests an interchange of the literature assignments of the two modes nu27 and nu29 in the IR spectrum and a different origin to the doublet of bands in the Raman spectrum at 883 and 897 cm(-1).     

Gas phase infrared spectrum and ab initio calculations of phosphorus(III) thiocyanide, SPCN

An attempt has been made to record the gas phase infrared spectrum of phosphorus(III) thiocyanide, SPCN, for the first time. The molecule was generated by an on-line process using phosphorus(III) thiochloride, SPCl, as a precursor passed over heated silver cyanide at about 350 degrees C. The products were characterized by the infrared spectra of their vapors. The low resolution gas phase Fourier transform infrared spectrum shows three of six characterized fundamental modes of SPCN within the range of the spectrometer used at 2151, 743 and 622 cm(-1) These three bands were assigned to nu(1)(C[triple bond]N stretch), nu(2)(S=P stretch), and nu(3)(C--P stretch), respectively. Ab initio self-consistent-field (SCF) molecular orbital (MO) and M?ller-Plesset second-order perturbation theory (MP2) calculations were performed to determine the geometry, total energy and the vibrational frequencies of SPCN.     

High-resolution absorption spectrum of jet-cooled CH3Cl between 70,000 and 85,000 cm(-1): new assignments

The absorption spectrum of jet-cooled CH(3)Cl was photographed from 165 to 117 nm (or 60,000 - 85,000 cm(-1), 7.5-10.5 eV) at a resolution limit of 0.0008 nm (0.3-0.6 cm(-1) or 0.04-0.08 meV). Even in the best structured region of the spectrum, from 70,000 to 85,000 cm(-1) (8.7-10.5 eV), observed bandwidths (full width at half maximum) are large, from 50 to 150 cm(-1). No rotational feature could be resolved. The spectrum is dominated by two strong bands near 9 eV, 140 nm, the D and E bands of Mulliken [J. Chem. Phys. 8, 382 (1940)] or the spectral region D of Price [J. Chem. Phys.4, 539 (1936)]. Their relative intensity is incompatible with previous assignments, namely, to a triplet and a singlet state belonging to the same configuration. On the basis of the present ab initio calculations, those bands are now assigned to two singlet states, the (1)A(1) and (1)E excited states resulting from the 2e(3)4pe Rydberg configuration. The present calculations also reveal that the two (1)E states issued from 2e(3)4sa(1) and 2e(3)4pa(1) are quasidegenerate and strongly mixed. They should be assigned to the two broad bands near 8 eV, 160 nm, the B and C bands of Mulliken and Price. Three vibrational modes are observed to be active: the CCl bond stretch nu(3)(a(1)), and the CH(3) umbrella and rocking vibrations, respectively, nu(2)(a(1)) and nu(6)(e). The fundamental frequencies deduced are well within the ranges defined by the corresponding values in the neutral and ion ground states. The possibility of a dynamical Jahn-Teller effect induced by the nu(6)(e) vibrational mode in the (1)E Rydberg states is discussed.     

Comparative study of infrared and Raman spectra of CCl4 in vapour and condensed phases: effect of LO-TO splitting resulting from hetero-isotopic TD-TD interactions

Salient features of an in-depth comparative study of infrared and Raman spectra of CCl(4) in vapour, liquid and condensed phases are presented. Wavenumbers of nu(4), nu(1)+nu(4), nu(3) and 2 nu(3) modes of CCl(4) vapour in infrared and Raman spectra are found to be in good agreement. Analysis of the vibrational spectra of liquid CCl(4) together with the spectroscopic observations on solid CCl(4) at low temperatures reveal TD-TD interaction amongst various CCl(4) isotopes in condensed states. The concept of LO-TO splitting of dipole active nu(3) and nu(1)+nu(4) Fermi doublet have been invoked to explain several features of the vibrational spectra of liquid CCl(4). There is significant strengthening of Fermi resonance interaction between nu(3) and nu(1)+nu(4) modes of CCl(4) in condensed phases relative to that in vapour phase. The Fermi resonance interaction parameter W has been found to be independent of molecular environment.     

A study of the mode-selective trans--cis isomerization in HONO using ab initio methodology

Ab initio calculations on the six-dimensional cis--trans double minimum potential energy surface of the electronic ground state of the HONO molecule were performed using a coupled cluster approach. An analytic fit to the data points was established. The interconversion barrier was calculated to be 4105 cm(-1). The nuclear motion problem was solved variationally using a full six-dimensional Hamiltonian in internal coordinates. The eigenstates up to about 3650 cm(-1) were tentatively assigned by harmonic quantum numbers. The assignment was based on the mean values of the internal coordinates of the six-dimensional eigenfunctions and on a comparison of the eigenenergies with those calculated by second-order perturbation theory from a full quartic force field in dimensionless normal coordinates. In cold matrices the trans- and the cis-OH nu(1) stretching modes and the first trans- and cis-NO 2nu(2) stretching overtones lead to isomerization. In the isolated molecule these modes (J=0) were found to be entirely localized. However, several overtones of the nu(4) ONO bending and nu(5) N-O stretching, which are close in energy to the OH stretch and combined with the torsional mode, were found to be strongly cis-trans delocalized.