ELECTRIC FIELD-INDUCED SPECTRA AND DIPOLE MOMENT OF THE $A^{1}A_{2}$ STATE OF FORMALDEHYDE.

Abstract

$^{1}$ A. D. Buckingham and D. A. Ramsay, J. Chem. Phys. 42, 3721 (1965). $^{2}$ N. J. Bridge and D. A. Dows, paper 16, Columbus Symposium 1966. $^{3}$N. J. Bridge, D. A. Haner, and D. A. Dows, J. Chem. Phys. 43, 3128 (1966).Author Institution: Department of Chemistry University of Southern California, Los Angeles, California, 90007``Electric field spectra'' are obtained by modulating the ultraviolet absorption spectrum of a gas by an alternating electric field applied to the $sample,^{1,2,3}$ A lock-in amplifier detects the signal induced at even harmonics of the applied field frequency. The amplitudes and line shapes of the EFS lines depend on the molecular dipole moments in both electronic states. A quantitative treatment of the EFS phenomenon has been applied to lines of the $3390 {\AA}$ band of formaldehyde, and the excited state moment obtained at $\mu^{\prime}=1.52 = .05D$. The method can be applied with slight modification to spectra which contain overlapping lines, and some results will be described. This research was supported by the National Science Foundation