Laser photoelectron spectroscopy of CH2−, and the singlet–triplet splitting in methylene
- 15 May 1981
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 74 (10) , 5460-5473
- https://doi.org/10.1063/1.440951
Abstract
Photodetachment of an electron from CH2− ions using visible light produces CH2 in both its ground 3B1 and lowest excited 1A1 states. In an earlier letter, this process was utilized to determine directly a singlet–triplet splitting of 19.5 kcal/mol. In this paper are reported the details of the early measurement and a number of additional investigations designed to test critically the earlier assignments. Data reported here indicate that one suggested problem with the early results, a misassignment of the 3B1 origin resulting from negative ion hot bands, is not likely. These new results do reveal the presence of an additional peak in the photoelectron spectrum which could possibly be the lowest level of the 3B1 state, allowing a singlet–triplet splitting of 19.5 or 23.2 kcal/mol. The results reported here do not indicate any other inconsistency in the original assignment. Finally, these data are discussed in light of the formidable body of theoretical and indirect thermochemical determinations suggesting a singlet–triplet splitting near 8 kcal/mol.Keywords
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