The A2E–X2A1 System of CaOCH3

Geometry of the CaOCH3 radical from isotope effects in the transition

“…1. It can be seen that there is a small red shift of <0.1 cm À1 when 13 C is substituted for 12 C, and a much larger shift of $10 cm À1 on substituting D for H. All four isotopomers showed a similar structure to that described in [1], and for the two hydride species, comparison of the spectra enabled the lines to be assigned in a straightforward manner. Because of their increased moments of inertia about both a and b axes, the deuteride spectra were more compact and their assignment was more challenging.…”

“…The techniques and programs that were used to fit the data are described in detail in [1]. We used the Hamiltonian of Endo et al [3] and Cerny et al [5] to calculate the energies of the upper 2 E and lower 2 A 1 states, respectively.…”

“…In a recent publication [1] we reported an analysis of high resolution spectra of theà 2 E-X 2 A 1 transition of CaO 12 CH 3 . The molecules were formed in a laser ablation source by reacting methanol with calcium vapour produced by ablating a calcium rod with the pulsed UV radiation from the third harmonic of a Nd:YAG laser.…”

“…From the complete set of rotational constants it should be possible to determine most of the structural parameters uniquely, and also to determine the effects (if any) of electronic excitation and isotopic substitution on the geometry of the methyl group. The experimental details were identical to those previously described [1].…”

Extended perturbation formulae for Jahn–Teller molecules

“…In contrast, the values for e aa in CaCH 3 [26] and CaOCH 3 [27] in the à 2 E state are very small, even smaller than for MgCH 3 (see above). This tells us that the Jahn-Teller interaction in these molecules is vanishingly small, in disagreement with the assignments reported in [28] and [9].…”