Infrared spectra of molecules and materials of astrophysical interest

The Raman spectra of gaseous, liquid and solid, and infrared spectra of gaseous and solid isopropylamine-d sub 0 and -d sub 2 was investigated between 4000 and 50 cm superscript -1. Differences between the spectrum of the solid phase and that of the fluid phases were interpreted in terms of an equilibrium between low energy s-trans and high energy gauche conformers, and a complete vibrational assignment was proposed for the s-trans conformer. The far infrared spectra of the gaseous compounds contained bands due to the asymmetric amino and coupled methyl torsions; the assignment of these bands was aided by observation of a number of two quantum transitions for each vibrational mode. The asymmetric potential functions were calculated, which resulted in values for the enthalpy differences between conformers in the gaseous phase of 446 and 523 callmole for the sub 0 -d and -d sub 2 compounds, respectively. The methyl torsional potential function of isopropylamine-d sub 0 was calculated which led to a value for the barrier height to internal rotation of the methyl rotors of 4.23 + or - 0.06 kcal/mole. Values for the ideal gas thermodynamic functions were calculated over a range of temperatures

Infrared spectra of molecules and materials of astrophysical interest Quarterly progress report, 15 jun. - 15 sep. 1970

Infrared spectra of molecules and materials of astrophysical interest Quarterly progress report, 15 Jun. - 15 Sep. 197

Infrared spectra of molecules and materials of astrophysical interest Quarterly progress report, 15 Dec. 1970 - 15 Mar. 1971

Vibrational spectra of molecules expected in Jovian atmospher

Infrared spectra of molecules and materials of astrophysical interest

The vibrational spectra from 4,000 to 33/cm of several molecules which may be present in the atmosphere of the Jovian planets or exist in outer space were studied. These studies have been made to provide vibrational frequencies which can be used to: (1) determine the composition of the cloud covers of several of the planets, (2) provide structural information under favorable circumstances, (3) provide necessary data from which accurate thermodynamic data can be calculated, and (4) furnish information as to the nature of the potential energy function of the molecules and forces acting within them. Some of the molecules studied can be produced photochemically from methane, ammonia, and hydrogen sulfide which are thought to be constituents of the planets with reducing atmospheres. Some of the compounds will polymerize under ultraviolet radiation and drop out of the atmospheres. However, planets with a hot base, like that of Jupiter, may rebuild molecules destroyed photochemically. These criteria were used in selecting the compounds under study

Infrared spectra of molecules and materials of astrophysical interest

The vibrational spectra from 4000 to 33 cm-1 of several modecules which may be present in the atmosphere of the Jovian planets are studied to provide vibrational frequencies which can be used to: (1) determine the composition of the cloud covers of several of the planets; (2) provide structural information under favorable circumstances; (3) provide necessary data from which accurate thermodynamic data can be calculated; and (4) furnish information as to the nature of the potential energy function of the molecules and forces acting within them. Some of the molecules are produced photochemically from methane, ammonia, and hydrogen sulfide which are thought to be constituents of the planets with reducing atmospheres. Some of the compounds polymerize under ultraviolet radiation and drop out of the atmospheres. However, planets with a hot base, like that of Jupiter, may rebuild molecules destroyed photochemically

Infrared spectra of molecules and materials of astrophysical interest Quarterly progress report, 15 Sep. - 15 Dec. 1970

Vibrational spectra of molecules and solid materials from 4000 to 33 cm in Jovian atmospher

Bond Properties and Molecular Conformation from Vibrational Intensity Analysis

Experimental vibrational intensities in infrared spectra can be transformed into quantities characterizing bond properties fol- lowing the formalism of the bond polar parameters model. The theory is briefly presented. An optimized set of bond polar parameters for hydrocarbons is obtained following constraints derived from experimental spectral data and ab initio MO calculations. The set of intensity parameters together with transferable force constants is used in predicting the infrared spectra of individual conformers and equilibrium conformer mixtures of n-butane-do, n-pentane-d, n-pentane-djj and n-hexane-d, The influence of rotational isomerism on infrared intensities in these systems is discussed

Far Infrared and Raman Spectroscopic Investigations of the Lattice:Modes of Crystalline Thiophene

Vibrational spectroscopic measurements combined with the lattice statics and lattice mod es calculations have been applied in order to derive the most probable structure of the low temperature (stable) phase V of thiophene (below 112 K). The far infrared spectrum has been recorded from 135 to 30 cm? of this phase of thiophene at 20 K. The low frequency Raman spectrum from 150 to 10 cm" has also been record ed for the phase V at 35 K. From the fact that there is coincidence between lattice mode frequencies observed in the infrared and Raman spectra, one can exclude centrosymmetric space groups. The observations of 20 lattice modes in the Raman spectrum and 14 modes in the FIR spectrum eliminate the possibility of tetragonal symmetry, but the data are consistent with orthorhombic symmetry with the unit cell containing 4 molecules on Cl sites. In spite of the glassy-like transition observed for this phase at 42 K, both spectra bear striking resemblance to the typical low frequency spectra of molecular crystals. Therefore, it is assumed, for the purposes of the static and dynamic studies, that the thiophene in phase V can be considered as an ideally ordered crystal. Calculations of the lattice energy and lattice mode frequencies, based on the atom-atom potential, appear to be most consistent with space group Pca2l (C2v5) which is in agreement with most of the earlier predictions made for the structure of the thiophene phase V. The Raman spectrum of the metastable phase II2 is also given

Far Infrared and Raman Spectroscopic Investigations of the Lattice:Modes of Crystalline Thiophene

Vibrational spectroscopic measurements combined with the lattice statics and lattice mod es calculations have been applied in order to derive the most probable structure of the low temperature (stable) phase V of thiophene (below 112 K). The far infrared spectrum has been recorded from 135 to 30 cm? of this phase of thiophene at 20 K. The low frequency Raman spectrum from 150 to 10 cm" has also been record ed for the phase V at 35 K. From the fact that there is coincidence between lattice mode frequencies observed in the infrared and Raman spectra, one can exclude centrosymmetric space groups. The observations of 20 lattice modes in the Raman spectrum and 14 modes in the FIR spectrum eliminate the possibility of tetragonal symmetry, but the data are consistent with orthorhombic symmetry with the unit cell containing 4 molecules on Cl sites. In spite of the glassy-like transition observed for this phase at 42 K, both spectra bear striking resemblance to the typical low frequency spectra of molecular crystals. Therefore, it is assumed, for the purposes of the static and dynamic studies, that the thiophene in phase V can be considered as an ideally ordered crystal. Calculations of the lattice energy and lattice mode frequencies, based on the atom-atom potential, appear to be most consistent with space group Pca2l (C2v5) which is in agreement with most of the earlier predictions made for the structure of the thiophene phase V. The Raman spectrum of the metastable phase II2 is also given

Combined BIMA and OVRO observations of comet C/1999 S4 (LINEAR)

We present results from an observing campaign of the molecular content of the coma of comet C/1999 S4 (LINEAR) carried out jointly with the millimeter-arrays of the Berkeley-Illinois-Maryland Association (BIMA) and the Owens Valley Radio Observatory (OVRO). Using the BIMA array in autocorrelation (`single-dish') mode, we detected weak HCN J=1-0 emission from comet C/1999 S4 (LINEAR) at 14 +- 4 mK km/s averaged over the 143" beam. The three days over which emission was detected, 2000 July 21.9-24.2, immediately precede the reported full breakup of the nucleus of this comet. During this same period, we find an upper limit for HCN 1-0 of 144 mJy/beam km/s (203 mK km/s) in the 9"x12" synthesized beam of combined observations of BIMA and OVRO in cross-correlation (`imaging') mode. Together with reported values of HCN 1-0 emission in the 28" IRAM 30-meter beam, our data probe the spatial distribution of the HCN emission from radii of 1300 to 19,000 km. Using literature results of HCN excitation in cometary comae, we find that the relative line fluxes in the 12"x9", 28" and 143" beams are consistent with expectations for a nuclear source of HCN and expansion of the volatile gases and evaporating icy grains following a Haser model.Comment: 18 pages, 3 figures. Uses aastex. AJ in pres