SPIN SPLITTINGS AND ROTATIONAL FINE STRUCTURE IN THE LOWEST TRIPLET STATE OF FORMALDEHYDE
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Date
1963
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Ohio State University
Abstract
“In earlier experimental $work,^{1}$ rotational fine structure in the singlet-triplet $(^{3}A_{2} \leftarrow ^{1}A_{1})$ absorption spectrum of formaldehyde was resolved by using low gas pressures in a multiple-pass absorption cell at -- $78^{\circ} C$. Because of the large number of lines in each band and the borderline nature of the resolution $(0.12\;cm^{-1})$, a number of nearly equivalent assignments in the low J range could be made. Their indistinguishability affected the rotational constant only slightly but presented difficulties in dealing with the spin splittings. The recent $avavilability^{2}$ of very accurate ground state energy levels for formaldehyde has removed much if the ambiguity in the analysis, and rotational constants and spin splittings have now been obtained for the $0^{+}$ and $1^{+}$ inversion levels of the triplet state. The main results of the analysis are: (1) the weak transition dipole lies along the CO axis; (2) transitions to triplet state levels for which $J = N \pm S$ are much stronger than those for which J = N; (3) the observed spin splittings are well described by the theory of Van $Yleck^{3}$ for an approximately symmetric rotor; and (4) the molecule is highly nonplanar in the triplet state.”
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$^{1}$G. W. Robinson and V. E. di Giorgio, Can. J. Chem., 36, 31 (1958); J. Chem. Phys., 31, 1678 (1959). $^{2}$H. G. Poole and J. E. Parkin, University College London (Unpublished results). $^{3}$J. H. Van Vleck, Rev, Mod. Phys., 23, 213 (1951).
Author Institution: Gates and Crellin Laboratories of Chemistry, California Institute of Technology
Author Institution: Gates and Crellin Laboratories of Chemistry, California Institute of Technology