High‐level ab initio calculations on HGeCl and the equilibrium geometry of the ùA″ state derived from Franck‐Condon analysis of the single‐vibronic‐level emission spectra of HGeCl and DGeCl

Abstract

CCSD(T) and/or CASSCF/MRCI calculations have been carried out on the X(1)A' and A(1)A'' states of HGeCl. The fully relativistic effective core potential, ECP10MDF, and associated standard valence basis sets of up to the aug-cc-pV5Z quality were employed for Ge. Contributions from core correlation and extrapolation to the complete basis set limit were included in determining the computed equilibrium geometrical parameters and relative electronic energy of these two states of HGeCl. Based on the currently, most systematic CCSD(T) calculations performed in this study, the best theoretical geometrical parameters of the X(1)A' state are r(e)(HGe) = 1.580 +/- 0.001 A, theta(e) = 93.88 +/- 0.01 degrees and r(e)(GeCl) = 2.170 +/- 0.001 A. In addition, Franck-Condon factors including allowance for anharmonicity and Duschinsky rotation between these two states of HGeCl and DGeCl were calculated employing CCSD(T) and CASSCF/MRCI potential energy functions, and were used to simulate A(1)A'' --> X(1)A' SVL emission spectra of HGeCl and DGeCl. The iterative Franck-Condon analysis (IFCA) procedure was carried out to determine the equilibrium geometrical parameters of the A(1)A'' state of HGeCl by matching the simulated, and available experimental SVL emission spectra of HGeCl and DGeCl of Tackett et al., J Chem Phys 2006, 124, 124320, using the available, estimated experimental equilibrium (r(e)(z)) structure for the X(1)A' state, while varying the equilibrium geometrical parameters of the A(1)A'' state systematically. Employing the derived IFCA geometry of r(e)(HGe) = 1.590 A, r(e)(GeCl) = 2.155 A and theta(e)(HGeCl) = 112.7 degrees for the A(1)A'' state of HGeCl in the spectral simulation, the simulated absorption and SVL emission spectra of HGeCl and DGeCl agree very well with the available experimental LIF and SVL emission spectra, respectively.

Franck-Condon simulation, including anharmonicity, of the photodetachment spectrum of P2H−: Restricted-spin coupled-cluster single-double plus perturbative triple and unrestricted-spin coupled-cluster single-double plus perturbative triple -F12x potential energy functions of P2H and P2H−

“…The IFCA procedure (see also Ref. 37), mentioned above and carried out in Refs. 3 and 4, has also been carried out in the present study.…”

“…In this connection, in the IFCA procedure, the geometrical parameters of one state have to be fixed usually to available experimental values, while those of the other state are varied based on the predicted directions of changes from ab initio calculations (see, for example, Ref. 37). However, in the present case, experimental geometrical parameters are unavailable for both states concerned.…”

Simulation of the single-vibronic-level emission spectrum of HPS

“…1. We have used our ab initio/FCF method [2][3][4] successfully to provide "fingerprint" type assignments of SVL emission spectra of numerous triatomic molecules, [5][6][7][8][9][10][11][12] including HPO/DPO, 13 which are valence iso-electronic with HPS/DPS. In addition, a) Authors to whom correspondence should be addressed.…”