Robert J. Thibault

High resolution infrared spectra of C212H2, C12C13H2, and C213H2☆

Abstract Two parallel bands in Fermi resonance, ν3, and ν2 + ν41 + ν51, have been studied in the 3200–3400 cm−1 region of C212H2. The calculated unperturbed frequencies for ν3 and ν2 + ν41 + ν51 are 3288.66 cm−1 and 3288.11 cm−1, respectively. The assignment of ν3 to the higher frequency transition is confirmed by the study of this diad in C13C12H2 and C213H2. In addition the absorption spectra of C13C12H2 and C213H2 have been obtained in the 2600–2800 cm−1, 3300–3400, and 6400–6600 cm−1 spectral regions. The unperturbed vibrational frequencies have been obtained for C13C12H2, and a few of these frequencies have been calculated for C213H2. Equilibrium B values have been obtained for the isotopic carbon molecules, and these values have been used to calculate accurate rc distances for acetylene. The “substitution structure” has also been calculated.

Analysis of Some Perturbations in the ν4 Band of Methyl Chloride

The ν4 band of CH3Cl has been analyzed in detail. It is found that there is a weak, but important, vibrational resonance between ν41 and 3ν61. The resonance is quantitatively taken into account in order to determine the unperturbed rotational constants for both ν41 and 3ν61. Both chlorine isotopes are resolved and treated separately. The interaction parameter is found to be given by 3.519( ± 0.006) + 0.028kl( ± 0.003) cm − 1 where the uncertainties are 3 times the computed standard errors. The k‐dependent term is evidently due to a z‐axis Coriolis‐like interaction which is also possible between ν41(E) and 3ν61(E).

Vibration–Rotation Bands of Deuterium Cyanide and Hydrogen Cyanide*

Six vibration–rotation bands of DCN between 2 and 6 μ have been analyzed. All the rotational constants have been obtained through the terms quadratic in vibrational quantum numbers. Two quadratic and seven cubic vibrational anharmonic constants have been obtained explicitly. Seven combinations of quadratic and cubic vibrational constants have also been obtained. Data are given on the analysis of the two parallel fundamental bands of D13CN, as well as the ν3 bands of DC15N, HI3CN, and HC15N. Δ–Δ transitions of both DCN and HCN in the ν3 fundamental regions have been analyzed. The splitting of the Δ levels was clearly observed for the first time and is in agreement with the l-type resonance calculations. The line structure of the Q branches of both Π–Π and Δ–Δ “hot bands” has also been resolved. By means of the Ritz principle the levels 2ν20, 2ν22, and ν21 of DCN and 2ν22 of HCN have been determined.

Rotational fine structure of the perpendicular band, ν7, of ethane

Abstract The perpendicular band, ν 7 , of ethane was studied, and individual lines were assigned in the subbands with K Δ K = +12 to −5. An improved set of ground state constants has been obtained, and upper state constants are reported for the individual subbands.

Infrared‐Emission Spectrum of HBr Excited in an Electric Discharge. Determination of Molecular Constants

The infrared‐emission spectra of H79Br and H81Br have been observed by exciting HBr in an electric discharge. Lines in the 1–0, 2–1, and 3–2 bands have been measured to an accuracy of the order of 0.01 cm−1. Pure rotational transitions of H79Br and H81Br which were not resolved have also been observed and measured with an accuracy of the order of 0.2 cm−1. Values are reported for ωe, ωexe, ωeye (only limits for this constant), Be, De, αe, βe, γe, δe, and approximate values of H0 and H1 are also obtained. The results are found to be in agreement with Dunhams theory. Values of the potential constants a1, a2, and a3 are calculated. The Be values for H79Br and H81Br agree with calculations based on microwave measurements of D79Br and D81Br.

Pressure Broadening of DCl by HCl and of HCl by DCl. A Comparison of Experimental Results with Anderson's Theory

Linewidths in the 1–0 band of DCl broadened by HCl and in the 1–0 band of HCl broadened by DCl are reported for rotational levels up to | m | = 15 and 13, respectively. These experimental results are compared with calculated values using Andersons theory as amplified by Tsao and Curnette. Calculations are made at 300°K for quadrupole moments of 2, 4, and 6 D·A and calculations at 194.5°K are also made for a Q of 6 D·A.

ABSORPTION BANDS OF CARBON DIOXIDE FROM 5.3 TO 4.6 MICRONS

Measurements have been made of the frequencies of the infrared absorption lines of CO2 in the region from 1850 cm−1 to 2150 cm−1. Observations were made at various pressures and pathlengths up to a maximum of 72 meter-atmospheres. Vibration-rotation constants were obtained characterizing the transitions 111c0–000, 111d0–000, 031c0–000, 031d0–000, 200–011c0, I22c0–011c0, 122d0–011d0 for C12O2. The 111c0–000 band due to the C13O2 molecule was also measured.

Broadening of the ν 3 Lines of HCN Due to Argon, Carbon Dioxide, and Hydrogen Chloride*

The pressure broadening effect of argon, carbon dioxide, and hydrogen chloride on the ν3 band of HCN has been measured. The broadening effects of the different gases are found to be in qualitative agreement with the theory. Of particular importance is the observation of an oscillatory behavior in the J dependence of the line half-width for HCl+HCN. This oscillatory behavior is explained as due to a dipole-dipole interaction for which the large difference between the rotational levels of perturber and absorber molecules causes some levels to be in resonance while others are not.