High-resolution absorption spectrum of jet-cooled CH3Cl between 70 000 and 85000cm−1: New assignments

The absorption spectrum of jet-cooled CH3Cl was photographed from 165to117nm (or 60000–85000cm−1, 7.5–10.5eV) at a resolution limit of 0.0008nm (0.3–0.6cm−1 or 0.04–0.08meV). Even in the best structured region of the spectrum, from 70000to85000cm−1 (8.7–10.5eV), observed bandwidths (full width at half maximum) are large, from 50to150cm−1. No rotational feature could be resolved. The spectrum is dominated by two strong bands near 9eV, 140nm, the D and E bands of Mulliken [J. Chem. Phys. 8, 382 (1940)] or the spectral region D of Price [J. Chem. Phys.4, 539 (1936)]. Their relative intensity is incompatible with previous assignments, namely, to a triplet and a singlet state belonging to the same configuration. On the basis of the present ab initio calculations, those bands are now assigned to two singlet states, the A11 and E1 excited states resulting from the 2e34pe Rydberg configuration. The present calculations also reveal that the two E1 states issued from 2e34sa1 and 2e34pa1 are quasidegenerate and stro...