Triplet states of the amide group. Trapped electron spectra of formamide and related molecules
Trapped electron (TE) spectra are obtained using ion cyclotron resonance detection of scavenged electrons. The lowest singlet-triplet transitions, 3(n→π*), in formamide (HCONH_2) and N,N-dimethyl formamide (HCONMe_2) are found at vertical energies of 5.30 and 5.00 eV, respectively. An unresolved band containing the 3(π→π*) and 3(n→3s) states appears at higher energies, centered at 6.60 and 6.00 eV, respectively. The TE spectra of formaldehyde (HCHO), acetaldehyde (MeCHO) and acetone (Me2CO) are obtained for comparison and are used along with results from ab initio theoretical calculations in establishing assignments. Singlet-triplet transitions dominate the spectra of all of these carbonyl containing molecules, to the exclusion of low lying singlet-singlet transitions. This is in agreement with other TE spectra and the expectation that (dσ/dE) will be higher near threshold for singlet-triplet as compared to singlet-singlet transitions.
© 1975 Published by Elsevier B.V. Received 9 July 1975. This research was supported in part by the United States Energy Research and Development Administration under Grant No. AT(04-03)767-8. The instrument used in these studies was funded by the National Science Foundation under Grant No. NSF-GP-18383.