Vibrational vave-packet dynamics in CV670 investigated by broadband femtosecond TR-CARS spectroscopy

Broadband femtosecond time-resolved coherent anti-Stokes Raman scattering ((TR-CARS)) is utilized to investigate the wave-packet dynamics of Cresyl Violet (CV670) dye molecules in ethanol solvent at room temperature. An interesting behavior of wave-packet dynamics phenomena is observed and discussed for the first time, and several unknown Raman vibrational modes with frequency differences of 32 cm⁻¹, 38 cm⁻¹, 45 cm⁻¹, 50 cm⁻¹, 55 cm⁻¹, 65 cm⁻¹, 80 cm⁻¹, 95 cm⁻¹ and 101 cm⁻¹ are excited and obtained at the same time. This work makes possible high efficiency in the structure investigation as well as dynamics of intra-molecular processes by broadband femtosecond (TR-CARS) spectroscopy with fast Fourier transformation (FFT) analysis means.     

Raman spectra of single crystal Li2SeO4

The room temperature polarized Raman spectra of single crystal Li₂SeO₄ are assigned using a factor group analysis. The internal optic modes of the selenate ion are responsible for Raman bands from 920 to 440 cm⁻¹, the translational optic modes of the lithium occur in the interval from 444 to 290 cm⁻¹ and the external optic modes of the selenate ion are found between 210 and 70 cm⁻¹. The symmetry-based assignments of these bands are discussed.     

Fourier transform Raman spectroscopy of kandite clays

The Raman spectra of the kandite clay minerals, kaolinite, halloysite, dickite and nacrite, have been measured in the 180–3000 cm⁻¹ region using Fourier transform near-IR Raman spectroscopy. These clays have a very small Raman cross-section and long data collection times were often required to obtain good spectra. Each clay has its own unique characteristic Raman spectrum which enables each kandite to be identified easily. In contrast, it is quite difficult to distinguish kandite clays by IR spectroscopy. Nacrite and dickite have relatively intense Raman peaks in the 1000–1100 cm⁻¹ region, whereas kaolinite is characterized by an intense peak at 685 cm⁻¹ and halloysite at 470 cm⁻¹.     

The low-frequency Raman and IR spectra of nitric acid hydrates

The low-frequency region of the infrared and Raman spectra of nitric acid hydrates is analyzed. Theoretical calculations of the vibrational normal modes of the crystals of nitric acid monohydrate and the β-phases of the dihydrate and trihydrate are carried out, focusing the results in the regions below 175 cm⁻¹ and near the symmetric stretch of the nitrate ion NO₃⁻, around 1000–1100 cm⁻¹. A prediction of the corresponding infrared spectra is presented. A joint study is performed of the calculated normal modes, the predicted IR spectra, and the recently published Raman spectra of these compounds, based on symmetry considerations and using the atomic displacements associated to each normal mode as a further source of information. Although most of the modes present a strong mixture of atomic motions, assignments can be proposed for some of the vibrations.     

Vibrational spectra of halogen substituted cyclopropanes—V. Trans-1,2-dichlorocyclopropane

The i.r. spectra of gaseous trans-1,2-dichlorocyclopropane were measured from 4000 to 400 cm⁻¹ and to 200 cm⁻¹ in the liquid phase. The Raman spectrum of the liquid was obtained from 4000 to 50 cm⁻¹. An assignment of all 21 normal vibrations was proposed on the basis of i.r. vapour phase band contours, Raman depolarization ratios, expected group frequencies and comparison with closely related molecules. There is excellent agreement with the normal modes previously assigned for the cis and trans isomers of the chloro, bromo and iodo analogues. The data indicate little interaction between the two CHCl moieties.     

Surface-enhanced Raman spectroscopy of 2,5-dibromopyridine and 2,6-dibromopyridine

The surface-enhanced Raman spectroscopy of 2,6-dibromopyridine and 2,5-dibromopyridine in silver hydrosol has been studied. A satisfactory correlation has been observed between the normal Raman spectra in aqueous solution and their surface-enhanced Raman (SER) spectra in silver hydrosol. The prominent features in the SER spectra of the compounds are the strongly enhanced peaks at 1175 and 1369 cm⁻¹ due to (py)CBr and (CC,CN)(py) stretching vibrational modes respectively in 2,6-dibromopyridine and almost no enhancement of intensities in those vibrations in 2,5-dibromopyridine.     

Raman Optical Activity of Glucose and Sorbose in Extended Wavenumber Range

Raman optical activity (ROA) is pursued as a promising method for structural analyses of sugars in aqueous solutions. In the present study, experimental Raman and ROA spectra of glucose and sorbose obtained in an extended range (50–4000 cm⁻¹) are interpreted using molecular dynamics and density functional theory, with the emphasis on CH stretching modes. A reasonable theoretical basis for spectral interpretation was obtained already at the harmonic level. Anharmonic corrections led to minor shifts of band positions (up to 25 cm⁻¹) below 2000 cm⁻¹, while the CH stretching bands shifted more, by ∼180 cm⁻¹, and better reproduced the experiment. However, the anharmonicities could be included on a relatively low approximation level only, and they did not always improve the harmonic band shapes. The dependence on the structure and conformation shows that the CH stretching ROA spectral pattern is a sensitive marker useful in saccharide structure studies.     

Far infrared and low frequency gas phase Raman spectra,vibrational assignment,and conformational stability of 1-chloro-2-methylpropane and 1-bromo-2-methylpropane

The Raman (3200—10cm⁻¹) and infrared (3200—50 cm⁻¹) spectra of gaseous and solid 1-chloro-2-methylpropane and 1-bromo-methylpropane, as well as the Raman spectra of the liquids, have been recorded and assigned. The gauche asymmetric torsion of the 1-chloro-2-methylpropane molecules has been observed at 110 cm⁻¹ in the Raman spectrum of the gas. For the 1-bromo-2-methylpropane molecule, both the trans and gauche asymmetric torsions have been observed at 106.70 and 103.94 cm⁻¹, respectively, along with three additional transitions for the gauche conformer. From these data, the asymmetric potential function for the bromide molecules to V₁ = —493 ±16, V₂ = 595 ± 18, and V₃ = 2006 ± 6 cm⁻¹ with the trans conformer being more stable than the gauche conformer by 44 ± 20 cm⁻¹. The trans form is found experimentally to be more stable in the liquid phase by 30 ± 14 cm⁻¹ (83 ± 40 cal mol⁻¹). From the relative intensities, in the Raman spectra, of the CCl stretches measured as a function of temperature, the gauche conformer of the chloride molecules to be 167 ± 71 cm⁻¹ (479 ± 203 cal mol⁻¹) more stable than the trans conformer in the gas phase, and 73 ± 10 cm⁻¹ (208 ± 29 cal mol⁻¹) more stable in the liquid phase. The methyl torsions for the gauche and trans conformers of both molecules are tentatively assigned in the gas phase and the barriers have been calculated. The results of this study are compared with previous studies on these molecules.     

Normal coordinate analysis of trans-stilbene and tolane

The vibrational frequencies and modes of trans-stilbene and tolane have been calculated using a simplified overlay valence force field previously developed for a series of smaller conjugated molecules. The force constants have been directly transferred assuming that the large molecules can be regarded as weakly coupled systems. Several unexpected changes in frequencies and modes on isotopic substitution are discussed, the most interesting ones occurring in the Raman spectrum of α,α′-¹³C substituted trans-stilbene. On the basis of the calculations many revisions in the assignments have been made. The rms frequency deviations are 8.0 cm⁻¹ and 6.9 cm⁻¹ for trans-stilbene and tolane, respectively.     

Vibrational spectroscopic characterization of the phosphate mineral series eosphorite–childrenite–(Mn,Fe)Al(PO4)(OH)2·(H2O)

The phosphate mineral series eosphorite–childrenite–(Mn,Fe)Al(PO₄)(OH)₂·(H₂O) has been studied using a combination of electron probe analysis and vibrational spectroscopy. Eosphorite is the manganese rich mineral with lower iron content in comparison with the childrenite which has higher iron and lower manganese content. The determined formulae of the two studied minerals are: (Mn_0.72,Fe_0.13,Ca_0.01)(Al)_1.04(PO₄, OHPO₃)_1.07(OH_1.89,F_0.02)·0.94(H₂O) for SAA-090 and (Fe_0.49,Mn_0.35,Mg_0.06,Ca_0.04)(Al)_1.03(PO₄, OHPO₃)_1.05(OH)_1.90·0.95(H₂O) for SAA-072. Raman spectroscopy enabled the observation of bands at 970 cm⁻¹ and 1011 cm⁻¹ assigned to monohydrogen phosphate, phosphate and dihydrogen phosphate units. Differences are observed in the area of the peaks between the two eosphorite minerals. Raman bands at 562 cm⁻¹, 595 cm⁻¹, and 608 cm⁻¹ are assigned to the ν₄ bending modes of the PO₄, HPO₄ and H₂PO₄ units; Raman bands at 405 cm⁻¹, 427 cm⁻¹ and 466 cm⁻¹ are attributed to the ν₂ modes of these units. Raman bands of the hydroxyl and water stretching modes are observed. Vibrational spectroscopy enabled details of the molecular structure of the eosphorite mineral series to be determined.     

Vibrational analysis of the imidazolate ring

IR and Raman spectra have been investigated for imidazolate and 4-methylimidazolate including five and three deuterated analogs, respectively. Assignment of the observed IR and Raman bands has been made on the basis of isotopic frequency shifts, Raman polarization properties, and normal coordinate calculations. The calculated normal frequencies are in good agreement with experimental ones: the average error below 1600 cm⁻¹ is 4.5 cm⁻¹ for 104 in-plane vibrations and 3.8 cm⁻¹ for 43 out-of-plane vibrations. The calculated vibrational modes are useful in analyzing the Raman bands of histidine residues in proteins.     

Raman spectra of single crystal Na2(SeO4)0.15(SO4)0.85

The room temperature polarized Raman spectra of single crystal Na₂(SeO₄)_0.15(SO₄)_0.85 are assigned, based on a factor group analysis. The internal optic modes of the oxyanions are responsible for Raman bands from 113O to 350 cm⁻¹ and the external optic modes are found between 270 and 50cm⁻¹. The symmetry-based and anion isotope abundance-based assignments of these bands are discussed.     

Infrared and Raman spectra of CuCl2·2(H,D)2O and K2CuCl4·2(H,D)2O. Vibrational modes,assignment and coupling of the water librations

The i.r. and Raman spectra of CuCl₂·2H₂O and K₂CuCl₄·2H₂O and of deuterated samples of these compounds are presented in the range 50–1700 cm⁻¹ at liquid helium, liquid nitrogen, and ambient temperatures. The spectra obtained are discussed and compared with the literature data in terms of both bonding structure of the water molecules and vibrational modes, assignment, intermolecular coupling, and combination bands of the H₂O, HDO, and D₂O librations. The i.r. and Raman bands of the librational modes of CuCl₂·2H₂O are very broad even at liquid helium temperature indicating orientational disorder of the water molecules.     

Infrared and Raman spectra of magnesium ammonium phosphate hexahydrate (struvite) and its isomorphous analogues. IX: Spectra of protiated and partially deuterated cubic magnesium caesium phosphate hexahydrate

Infrared and Raman spectra of cubic magnesium caesium phosphate hexahydrate, MgCsPO₄·6H₂O (cF100), and its partially deuterated analogues were analyzed and compared to the previously studied spectra of the hexagonal analogue, MgCsPO₄·6H₂O (hP50). The vibrational spectra of the cubic and hexagonal dimorphic analogues are similar, especially in the regions of HOH stretching and bending vibrations. In the difference IR spectrum of the slightly deuterated analogue (<5% D), one distinctive band appears at 2260 cm⁻¹ with a small shoulder at around 2170 cm⁻¹, but only one band is expected in the region of the OD stretchings of isotopically isolated HDO molecules. The small weak band could possibly result from second-order transitions (a combination of HDO bending and some libration of the same species) rather than statistical disorder of the water molecules. By comparing the IR spectra in the region of external vibrations of water molecules of the protiated compound recorded at RT (room temperature) and at LNT (liquid nitrogen temperature) and those in the series of the partially deuterated analogues, it can be stated with certainty that the bands at 924 and 817 cm⁻¹ result from librations of water molecules, rocking and wagging respectively. And the band at 429 cm⁻¹ can be safely attributed to a stretching Mg–O_w mode. In the ν₃(PO₄) and ν₄(PO₄) region in the infrared spectra, one band in each is observed, at 995 and 559 cm⁻¹, respectively. In the region of the ν₁ modes, in the Raman spectrum of the protiated compound, one very intense band was observed at 930 cm⁻¹ which is only insignificantly shifted to 929 cm⁻¹ in the spectrum of the perdeuterated compound. The band at 379 cm⁻¹ in the Raman spectrum could be assigned to the ν₂(PO₄) modes. With respect to the phosphate ion vibrations, the comparison between the two polymorphic forms of MgCsPO₄·6H₂O and their deuterated compounds shows that ν₁(PO₄) and ν₃(PO₄) appear at lower wavenumbers in the cubic phase than in the hexagonal phase. These data are in full agreement with the lower repulsion potential at the cubic lattice sites compared with that for the hexagonal lattice sites.     

Vibrational spectroscopic study of syngenite formed during the treatment of liquid manure with sulphuric acid

Syngenite (K₂Ca(SO₄)₂·H₂O), formed during treatment of manure with sulphuric acid, was studied by infrared, near-infrared (NIR) and Raman spectroscopy. C_s site symmetry was determined for the two sulphate groups in syngenite (P2₁/m), so all bands are both infrared and Raman active. The split ν₁ (two Raman+two infrared bands) was observed at 981 and 1000 cm⁻¹. The split ν₂ (four Raman+four infrared bands) was observed in the Raman spectrum at 424, 441, 471 and 491 cm⁻¹. In the infrared spectrum, only one band was observed at 439 cm⁻¹. From the split ν₃ (six Raman+six infrared) bands three 298 K Raman bands were observed at 1117, 1138 and 1166 cm⁻¹. Cooling to 77 K resulted in four bands at 1119, 1136, 1144 and 1167 cm⁻¹. In the infrared spectrum, five bands were observed at 1110, 1125, 1136, 1148 and 1193 cm⁻¹. From the split ν₄ (six infrared+six Raman bands) four bands were observed in the infrared spectrum at 604, 617, 644 and 657 cm⁻¹. The 298 K Raman spectrum showed one band at 641 cm⁻¹, while at 77 K four bands were observed at 607, 621, 634 and 643 cm⁻¹. Crystal water is observed in the infrared spectrum by the OH-liberation mode at 754 cm⁻¹, OH-bending mode at 1631 cm⁻¹, OH-stretching modes at 3248 (symmetric) and 3377 cm⁻¹ (antisymmetric) and a combination band at 3510 cm⁻¹ of the H-bonded OH-mode plus the OH-stretching mode. The near-infrared spectrum gave information about the crystal water resulting in overtone and combination bands of OH-liberation, OH-bending and OH-stretching modes.     

Assignment and anharmonicity analysis of overtone and combination bands observed in the resonance Raman spectra of carotenoids

The resonance Raman spectra of all-trans carotenoids have been observed in the region of 5000-500 cm⁻¹ for samples in glassy solution at 77 K and in the in vivo state at room temperature. Prominent bands in the wavenumber region higher than 2000 cm⁻¹ are assigned to either overtones or combinations of three modes due to skeletal stretches and the CH₃ in-plane rock. From the wavenumbers of the observed Raman bands, anharmonicity constants for these three modes (including cross-term constants) are obtained. It is found that, for each carotenoid studied, the cross-term anharmonicity constant between the CC and CC stretches is significantly larger than the other anharmonicity constants.     

Polarised single crystal Raman spectroscopy of sinhalite,MgAlBO4

Polarised single-crystal Raman spectra for sinhalite have been collected at 80 K over the range 1300-10 cm⁻¹. All 36 of the first-order Raman bands predicted by the factor group analysis (FGA) of the olivine structure type have been observed and assigned. Sinhalite has the smallest unit cell volume of any crystal with the olivine structure and is significantly more distorted than are the silicate olivines. This leads to distortion-related consequences in the vibrational spectra, such as greater wavenumber ranges for each type of mode and reduced Raman intensity for symmetric BO₄ modes. Intense Raman bands in the region 796-468 cm⁻¹ are assigned to BO₄ rotations/translations which deform the AlO bond without displacement of the aluminium atoms which lie on the M1 sites. Raman-active modes involving M1 cation displacements are incompatible with the FGA.     

Vibrational modes of the anthracene—tetrachlorophthalic anhydride charge-transfer complex

Raman and i.r. studies of the anthracene—tetrachlorophthalic anhydride charge-transfer complex have been carried out. Five lattice modes are identified in the low-frequency Raman spectra. The 21 cm⁻¹ lattice band is tentatively assigned to the librational vibration of the donor and acceptor molecules along their stacking axis. The intramolecular modes are assigned on the basis of the free-molecule symmetries D_2h and C_2ν for anthracene and tetrachlorophthalic anhydride, respectively. The intramolecular frequencies do not change significantly on complexation. This suggests that the molecular symmetry and the force constants between interacting molecules are not greatly affected by the formation of the complex.     

Vibrational spectra and normal coordinate analysis of p-cresol and its deuterated analogs

I.r. and Raman spectra of p-cresol and its seven deuterated analogs were investigated in dilute solutions of hydrophobic solvents. Assignments of the observed i.r. and Raman bands were made on the basis of isotopic frequency shifts, Raman polarization properties, i.r. intensifies and normal coordinate calculations. The calculated normal frequencies are in good agreement with the experimental ones: the average error below 1700 cm⁻¹ is 3.8 cm⁻¹ for 164 in-plane vibrations and 3.3 cm⁻¹ for 59 out-of-plane vibrations. The calculated vibrational modes may be useful in analysing the vibrational spectra of tyrosine. It is suggested that several doublets due to Fermi resonance and a trio of Raman bands in the 1260-1160 cm⁻¹ region are potential probes for the micro-environments of tyrosine side chains in proteins.     

Fourier-transform Raman and infrared spectra and normal coordinate analysis of (C6H5)2BiCl and [N(CH3)4]+[(C6H5)2BiCl2]−

The vibrational properties of the diphenylbismuth(III) chloride compounds (C₆H₅)₂BiCl and [N(CH₃)₄]⁺[(C₆H₅)₂BiCl₂]⁻ have been investigated. A comprehensive assignment of the fundamental modes in the measured Fourier-transform Raman and infrared spectra has been carried out. Normal coordinate calculations of these compounds based on new X-ray crystal structure data have been performed to identify the BiCl stretching and bending vibrations of both compounds. For [N(CH₃)₄]⁺[(C₆H₅)₂BiCl₂]⁻ in the solid state, the ν_s(BiCl₂) and ν_as(BiCl₂) occur at 215 cm⁻ (Raman) and 237 cm⁻ (Raman), respectively, in good agreement with the calculated wavenumbers. The force constant calculation yields a BiCl stretching force constant of 0.89 × 10² N m⁻¹.