The Raman Spectrum of Boron Trifluoride Gas

The Raman spectrum of BF3 was photographed using a purified preparation obtained from the thermal decomposition of C6H5N2BF4. Of the lines observed, that with the frequency 888 cm^—1 is certainly, and the band at 439–513 cm^—1 is probably due to BF3. The Raman frequencies and the infra-red results of Bailey et al. are assigned to the fundamental modes of vibrations

The Raman Spectra of Carbon and Silicon Tetrafluorides

We have photographed the Raman spectra for the tetrafluorides of carbon and silicon in both the liquid and gaseous states. The results are presented in Table I together with the Raman frequencies for CCl4 for purposes of comparison

The Raman Spectra of Boron Trifluoride, Trichloride, and Tribromide. The Effect of the Boron Isotopes

The Raman frequencies v1{1}, 2v2{2}, v3{2}, and v4{2} for BF3(g), BCl3(l), and BBr3(l) were found to be 886 and 783, 1394, 1038 and 1105, 440; 471, 924, 958 and 996, 243; 279, 743, 806 and 846, and 151 cm—1, respectively. The assignment of frequencies was determined by polarization experiments on BCl3 and is confirmed for the three compounds by the results of a normal coordinate treatment. The doubling of v1 in BF3 is ascribed to vibrational resonance between v1 and 2v4. The doubling of v3 in all three compounds is shown to be due to the presence of the two isotopes of boron B10 and B11. A satisfactory assignment of the infrared frequencies of BCl3 is made

Generalized oscillator strengths. Progress report, July 1, 1973--July 1, 1974

Progress is described on research under Contract AT(11-1)3247 and research still to be completed in the period July 1, 1973 to July 1, 1974. The research objectives defined in the original proposal were closely followed. The principal accomplishments during the period were: The introduction of a computer controlled counting system with provision for automatic control and operation of the electron spectrometer currently in use. Electron scattering with excitation of singlet-triplet transitions for helium was studied during the year both to acquire information on collision cross sections and to test a general theory of the abnormally high cross sections for forward scattering found for certain types of transitions. A theoretically predicted minimum in the cross section (at zero scattering angle) was found in a study over the range 100 to 500 eV of the 1/sup 1/S yields 2/sup 3/S transition of helium. Abnormally high cross sections for singlet-triplet transitions at high kinetic energy are predicted when the orbital term symbol is unchanged on excitation. As a test of the theory the X/sup 1/ SIGMA /sup +/ yields b/sup 3/ SIGMA /su p +/ transition in CO was looked for and found at THETA = 0 deg at both 200 and 300 eV thus confirming the theory. New electron scattering studies on both CO and CO/sub 2/ are described. A new method for the calculation of singlet-triplet energy differences from generalized oscillator strengths is described. (auth

INTENSITY DISTRIBUTION FOR THE X1Σ+→A1ΠX^{1}\Sigma^{+}\rightarrow {A}^{1}\Pi TRANSITION IN CARBON MONOXIDE EXCITED BY ELECTRON IMPACT∗IMPACT^{*}

$^{*}$The research reported in this paper has been sponsored by the Geophysics Research Directorate of the Air Force Cambridge Research Center, Air Research and Development Command. $^{1}$ E. N. Lassettre, A. S. Berman, S. Silverman and M. E. Krasnow, Bull. Am. Phys. Soc. 29 No. 4, 47 (1954) $^{2}$ S. A. Francis, Abstracts of Doctoral Dissertations, Ohio State University, No. 53, 207 (1946-47) $^{3}$ E. A. Jones, Abstracts of Doctoral Dissertations, Ohio State University, No. 56, 293 (1947-48) $^{4}$ E. Hutchisson, Phys. Rev. 36:410 (1930)Author Institution: Department of Chemistry, The Ohio State UniversityThe electron spectrometer described elsewhere1 has been used in a study of the excitation of the $X^{1}\Sigma^{+}(\nu^{\prime\prime}=o)\rightarrow {A}^{1}\Pi(\nu^{\prime}=\nu)$ transition in carbon monoxide by electron impact. Other work in this laboratory2,3 has already shown the close connection between excitation by radiation absorption and by electron impact. Resolution of the electron spectrometer is insufficient, in this case, to separate excitations to different vibrational levels. The envelope shape can, however, be compared with theoretical calculations when account is taken of energy spread in the electron beam and the finite resolution of the velocity analyzer. The envelope shape was determined experimentally by averaging six electron impact energy spectra taken at scattering angles from 3.4 to 8.4 degrees with an incident electron energy of 508 volts. In accord with theoretical predictions this envelope shape was independent of scattering angle. The energy distribution at the exit slit of the analyzer was obtained from measurements on helium. The theoretical calculations are based on harmonic oscillator wave functions in the ground and excited states. The theoretical results of Hutchisson4 have been used to calculate the relative transition probabilities. These transition moments are the same as are encountered in the theory of radiation absorption. Theoretical intensity distributions are in excellent agreement with experiment up to $\nu^{\prime} = 4$. At the higher levels the agreement becomes increasingly poorer, probably due to anharmonicity

THE ELECTRON IMPACT SPECTRA OF CH4CH_{4} AND CF4CF_{4}

$^{1}$ C.R. Brundle, M.B. Robin and H. Basch, J. Chem. Phys. 53, 2196 (1970).""Author Institution: Department of Chemistry, Carnegie-Mellon, University PittsburghThe electron impact spectra of the $CH_{4}$ and $CF_{4}$ have been studied with electrons having an incident energy of 400 eV and 500 eV and at scattering angles from $0^{\circ}$ to $5^{\circ}$. Comparison of these spectra with photo-electron spectra of the same $compounds^{1}$ indicates that several of the transitions in the electron impact spectra are members of Rydberg series for Rydberg orbitals of the carbon atom. In addition, this comparison suggests that the excited states of $CH_{4}$ are subject to a Jahn-Teller effect. The effect of this Jahn-Teller distortion of the excited state upon the differential cross section for electron scattering will be discussed. Present address of William R. Harshbarger: Bell Laboratories, Murray Hill, New Jersey 0797