The far infrared spectrum of nitroethane

The far infrared spectrum of nitroethane measured by Founer spectroscopy in the 8-60 cm^?1 is presented and interpreted in terms of a rigid frame-rigid top model for free internal rotation group. Ratational-internal rotational energy levels and absolute absorption intensities are calculated to first order for an optimal choice of molecule-fixed axes. The computed absorption based on a permanent dipole moment of 3.4 debye along the NC direction is in excellent agreement with the observed band.     

The resonance Raman spectrum of azulene

Excitation profiles have been measured for three Raman lines of azulene in CS₂ solution in the spectral range of the visible absorption system, viz. 665—570 nm. The results are unexpected in as much as the excitation profiles do not exhibit maxima at or near the absorption peaks. The results are interpreted on the basis of contributions to the A-term by other modes than the one studied in the Raman effect. These terms give rise to interferences which lower the excitation profile in some regions while causing maxima at other frequencies.     

The infrared spectrum of californium-249

The Cf-249 spectrum between 3700 and 12,000 cm^?1 has been recorded. The strongest 90 lines are listed.     

The infrared and Raman spectra of trans- and cis-tetrachloro-tetramethylbicyclopropylidene

The title compounds trans- and cis-2,2,2',2'-tetrachloro-3,3,3',3'-tetramethyl-bicyclopopylidene were synthesized, and their infrared and Raman spectra were recorded. Non-coincidence between the IR and Raman bands of the trans compound suggested C(2h) symmetry and a planar ring system. In the cis compound most of the IR and Raman bands coincided and a C(2v) symmetry seems likely. The exocyclic CC double bond gave rise to a medium/weak Raman band at 1,847 cm(-1) in the trans compound. In the cis derivative IR and Raman bands both at 1,825 cm(-1) were observed. From similarities with related molecules, the ring breathing, the antisymmetric ring stretch, the CCl(2) out-of-phase and in-phase stretch and the out-of-plane ring bending modes have been tentatively assigned for the trans and cis compounds.     

The infrared and Raman spectra of octachloro- and octabromocyclotetrasilane

The infrared and Raman spectra of cyclo-Si₄Cl₈ and cyclo-Si₄Br₈ have been measured and assigned. The selection rules indicate that the Si₄ ring is not planar. A normalcoordinate analysis (NCA) has been performed. The SiSi stretching-force constants are calculated to be 1.75–1.5·10² Nm^?1 and are lower than in the corresponding perhalogenated five- and six-membered rings. The SiCl and SiBr force constants seem to be somewhat higher (2.7–2.35·10² Nm^?1).     

The laser Raman and infrared spectra of crystalline dibenzyl

The Raman spectrum of crystalline dibenzyl has been excited with a 50-mw He-Ne laser (6328 Å) and thirty one Raman bands have been recorded. The far infrared spec trum which reveals six absorptions in the 10–270 cm⁻¹ region and the infrared spectrum from 300–3200 cm⁻¹ have been observed, and correlations with the Raman frequencies have been established. Assignments of some of the characteristic frequencies have been made, and the implications of the data regarding the geometry of the molecule are discussed.     

The identification of fibers by infrared and Raman microspectroscopy

The application of Raman and infrared microspectroscopy to fiber identification has been investigated. Natural and synthetic fibers, both organic and inorganic in nature, can be rapidly characterized by these techniques. In general, it has been found that infrared microspectroscopy offers a nonsubjective method of fiber identification that is quicker, easier, and occasionally, more selective than classical methods. Raman microspectroscopy has also been proven useful for these analyses. It provides low-frequency information, requires virtually no sample preparation, and supplies data complementary to that furnished by infrared microspectroscopy. In many cases one may use these methods for a quick differentiation of fibers of the same type which have undergone different chemical treatments.     

The resonance Raman spectrum of ultramarine blue

The resonance Raman spectrum of ultramarine blue has been observed by the use of 457.9, 488.0, 514.5, 568.2 and 647.1 nm excitation. With 457.9 nm excitation three progressions are observed; comparison of the results with earlier data from sulphur-doped alkali halide crystals indicates that ultramarine blue contains the S₂^? as well as the S₃^? anion.     

The Raman spectrum of hexamethylbenzene single crystal

A set of polarized Raman spectra obtained from suitable hexamethylbenzene single crystals at room temperature is presented. All the observed frequencies are attributed to intramolecular vibrations or lattice modes on the basis of clear polarization data.     

The far infrared spectrum of pyridine n-oxide

The two lowest internal modes of pyridine N-oxide and three of its lattice oscillations in the solid state at room temperature are reported for the first time on the basis of careful far infrared investigations from 33 to 525 cm^?1.     

The molecular structure and infrared and Raman spectra of SCCCS

The structure, rotational constants, and vibrational spectra of SCCCS have been predicted by ab initio and density functional quantum mechanical methods. Basis sets ranging in size from double-ζ plus polarization (DZP) to triple-ζ plus double polarization, augmented with f functions (TZ2Pf) were employed. Our theoretical results are in agreement with experiments for both the geometrical structure and most of the fundamental frequencies that have been observed. An exception occurs for the SCC bending frequency υ₅, for which the 1966 and 1972 assignments of Bates and Smith appear superior to the 1966 Smith and Leroi Raman assignment, accepted in the definitive recent studies of Holland and Winnewisser. We present results for four isotopomers of SCCCS that have not yet been observed in the laboratory.     

The infrared and Raman spectra of 2,4-and 2,5-dimethylbenzaldehydes

The vibrational frequencies of 2,4-and 2,5-dimethylbenzaldehydes have been reported from the study of ir absorption and Raman spectra of these molecules recorded in liquid phase. The probable assignments for all the frequencies are presented in terms of the fundamentals, overtones or combinations     

The polarized infrared spectrum of crystalline dimethyl oxalate

The polarized infrared spectra of oriented crystal films of dimethyl oxalate have been recorded at approximately 20 K. The symmetry species of the intramolecular modes have been determined on the basis of the polarization behavior of the observed bands and compared to the assignments made by previous workers by indirect methods. The Davydov components in some of the bands are observed and assigned to the infrared active factor group symmetry species A_u and B_u.     

The surface enhanced Raman spectrum of 2,6-lutidine

The surface enhanced Raman spectrum of 2,6-lutidine adsorbed on a polycrystalline Ag surface is reported along with a discussion of the effect on the methyl vibrations of adsorption on the electrode. The observation of an AgN stretch and small shifts of the methyl vibrations on the surface lead to a model of the molecule-surface interaction. If the molecule is adsorbed on a (100) or (110) face, surface roughness on an atomic scale is required to explain the observations. If the molecule is adsorbed on a (111) face, no surface roughness need be invoked. In either case a metalnitrogen bond somewhere between the van der Waals (physisorbed) and covalent (chemisorbed) limits is indicated.     

The infrared spectrum of Au-.CO2

The Au-.CO2 ion-molecule complex has been studied by gas phase infrared photodissociation spectroscopy. Several sharp transitions can be identified as combination bands involving the asymmetric stretch vibrational mode of the CO2 ligand. Their frequencies are redshifted by several hundred cm(-1) from the frequencies of free CO2. We discuss our findings in the framework of ab initio and density-functional theory calculations, using anharmonic corrections to predict vibrational transition energies. The infrared spectrum is consistent with the formation of an aurylcarboxylate anion with a strongly bent CO2 subunit.     

Raman and infrared spectroscopy of selected vanadates

Raman and infrared spectroscopy has been used to study the structure of selected vanadates including pascoite, huemulite, barnesite, hewettite, metahewettite, hummerite. Pascoite, rauvite and huemulite are examples of simple salts involving the decavanadates anion (V10O28)6-. Decavanadate consists of four distinct VO6 units which are reflected in Raman bands at the higher wavenumbers. The Raman spectra of these minerals are characterised by two intense bands at 991 and 965 cm(-1). Four pascoite Raman bands are observed at 991, 965, 958 and 905 cm(-1) and originate from four distinct VO6 sites. The other minerals namely barnesite, hewettite, metahewettite and hummerite have similar layered structures to the decavanadates but are based upon (V5O14)3- units. Barnesite is characterised by a single Raman band at 1010 cm(-1), whilst hummerite has Raman bands at 999 and 962 cm(-1). The absence of four distinct bands indicates the overlap of the vibrational modes from two of the VO6 sites. Metarossite is characterised by a strong band at 953 cm(-1). These bands are assigned to nu1 symmetric stretching modes of (V6O16)2- units and terminal VO3 units. In the infrared spectra of these minerals, bands are observed in the 837-860 cm(-1) and in the 803-833 cm(-1) region. In some of the Raman spectra bands are observed for pascoite, hummerite and metahewettite in similar positions. These bands are assigned to nu3 antisymmetric stretching of (V10O28)6- units or (V5O14)3- units. Because of the complexity of the spectra in the low wavenumber region assignment of bands is difficult. Bands are observed in the 404-458 cm(-1) region and are assigned to the nu2 bending modes of (V10O28)6- units or (V5O14)3- units. Raman bands are observed in the 530-620 cm(-1) region and are assigned to the nu4 bending modes of (V10O28)6- units or (V5O14)3- units. The Raman spectra of the vanadates in the low wavenumber region are complex with multiple overlapping bands which are probably due to VO subunits and MO bonds.     

Raman and infrared spectra of crystalline fluoroform

Raman and far-infrared spectra of crystalline fluoroform at temperatures between 20 and 106 K have been recorded. There is no evidence for any solid-state phase transitions, nor for hydrogen bonding. The rich lattice spectra and crystal field splittings suggest that the unit cell is rather large, and possible structures are discussed.     

Raman and infrared spectra of crystalline chloroform

Raman and far-infrared spectra of polycrystalline samples of chloroform at 20 and 80 K are reported. Crystal field spilttings of the intramolecular fundamentals are observed as well as nine Raman and six infrared lattice modes. Spectra are interpreted in terms of a group theoretical analysis based on the molecular and crystal symmetries.