No abstract

The microwave absorption spectrum of C6H5CHO has been investigated in the region 17.5–40.0 GHz and that for C6H5CDO in the region 26.5–40.0 GHz. Rotational transitions in the ground and first three excited torsional states in both molecular species have been identified. There is evidence for interaction of the second torsional state of C6H5CHO with another mode of vibration of the molecule. Accurate relative intensity measurements give the first torsional frequency of 113.8 ± 5.0 cm−1 for C6H5CHO and of 108.4 ± 4.25 cm−1 for C6H5CDO. The barriers to internal rotation of the aldehyde group calculated from these frequencies are 4.90 ± 0.43 and 5.28 ± 0.42 kcal/mole for C6H5CHO and C6H5CDO, respectively. The discrepancy between the observed and calculated values of inertial coefficients suggests the importance of vibration–rotation interaction in the theory of internal rotors with twofold potential barriers.

The linewidths of some 25 inversion spectral lines of ammonia in the frequency region of 18–29 kMc/sec have been measured. Corrections due to various effects such as source modulation, cell-length broadening, and Doppler shift were applied to the experimental data to evaluate the linewidth parameters. Self-broadening and foreign-gas broadening by some 15 different gases have been studied. In the case of self-broadening of the series of lines with J=K for which the effect of rotational resonance is negligible, the width parameters determined experimentally agree well with those calculated by Anderson's theory from (2, 2) to (5, 5), but appreciable deviations are found at higher J. For the lines with J≠K, the discrepancy becomes larger and increases with increasing difference between J and K. The quantum number dependence of the foreign-gas broadening by methyl chloride and by carbon dioxide has been investigated in detail. For methyl chloride broadening the theoretical and measured widths agree with each other to about the same extent as in self-broadening, whereas the agreement is somewhat less satisfactory in the case of carbon dioxide. An alternative formulation of the collision theory of line broadening is presented. Here the theory of radiation interruption is treated as a problem of multichannel collision. The essential feature of this formulation is that it includes the higher-order effects of the collision process rather than just the usual first-order terms. This analysis leads to suggestions as to possible directions of improving the calculations.

Im Mikrowellenspektrum von C6H5CHO (17,5‐40,0 GHz) und C6H5CDO (26,5‐40,0 GHz) wurden für beide Moleküle Rotationsübergänge in den Grundzustand und die drei ersten angeregten Torsionszustände identifiziert.

This d isserta tio n has been 61-2908 m icrofilm ed exactly as receiv ed RINEHART, Edgar A ., 1928-MEASUREMENT OF THE WIDTHS OF MICRO WAVE SPECTRAL LINES.The U n iversity of Oklahoma, P h .D ., 1961 P h y sic s, general