High resolution electronic spectroscopy of ZnCH3 and CdCH3

Abstract

Application of highresolution electron energy loss spectroscopy to the adsorption and the photoreaction of CH2I2 and CD3OD on a MoO x thin film ZnCH 3 and CdCH 3 radicals have been prepared in a coLd super.sonic free jet expansion and their laser-induced-fluorescence spectrum recorded for the A 2E<-X 2AI electronic transition. These spectra show well resolved rotational and spin structure, which has been completely analyzed. This !lnalysi~yields the rotational constants and the components of the spin-rotation tensors in the A and X states of both radicals. The observed constants are discussed in terms of the electronic structure of the radicals. It is demonstrated that the upper F2 spin-orbit component of the A 2E state of CdCH 3 is stronglY'perturbed by another, dissociative electronic state. This leads to some predissociation of the A 2E3/2 component and a broadening of its lines. The rotational and fine structure in this state is also quite perturbed leading to an unusual, but still interpretable spectrum.9376

Geometry of the CaOCH3 radical from isotope effects in the transition

“…For OCH 3 the angle reported was $110° [3,12], and the same value was obtained for SrOCH 3 [10] from an analysis in which A 00 was fixed at the OCH 3 value. The H Ĉ H bond angle was found to be $109.20°for ZnCH 3 and CdCH 3 [5]. Brazier and Bernath [11] give H Ĉ H = 105.6(±2.8)°i n the X state of CaCH 3 , and 109.2(±3)°in the à state, from analysis of electronic spectra.…”

“…For OCH 3 the bond angle increased by 4° [12], and for ZnCH 3 and CdCH 3 it increased by just over 3° [5], with estimated uncertainties of 2-4°. For SrOCH 3 a decrease of 2.7°was quoted for the HĈ H angle [10].…”

“…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. The fitting of the data was done in several stages.…”

The A2E–X2A1 System of CaOCH3

“…We shall only recall here the terms we have been using, following (20). Derivation of these terms can be found in (21, 22).…”

“…E = E(J , K ) − E 0 (K ) is the energy of the ground state rotational level, measured from the lowest rotational energy level having K = 0 if K = 3n, or from the lowest rotational energy level having K = 1 if K = 3n ± 1. This formula for E allows for nonequilibrium distributions between states of different nuclear spin symmetry (20). The method used by Cerny et al (20) projects the rotational eigenfunctions of the 2 A and 2 E electronic states upon the case (a) basis functions.…”