Ab initioMRD-CI study of the electronic spectrum of SiH

Abstract

Potential curves and other properties of the ground and excited states of Sill are calculated at close to full CI accuracy in DZP AO basis sets including f functions. The C 2N+ state of this system is shown to correspond to a second potential minimum of the B 2E+ species which occurs because of an avoided crossing with a dissociative state of the same symmetry. The D 2A and E 2)2+ states are assigned as members of Rydberg series involving upper orbitals of d8 and do symmetry respectively. In addition, a number of quartet states have been computed including the qI and two 4E-species which have apparently not yet been characterized experimentally. The 4H state is found to be strongly repulsive, causing predissociation of the 4s and 4p members of the lowest Rydberg series ; this observation is consistent with the fact that transitions to such upper states have yet to be observed experimentally. Computed spectroscopic constants, dipole and transition moments and dissociation energies are all found to agree quite well with ekperiment wherever comparison is possible, including results for spin-orbit constants as a function of vibrational level in the X 2IIr ground state. Comparison is also made with results for the isovalent systems PH +, CH and NH ÷ at various levels and it is noted that NH + exhibits a number of unusual features because of the relatively high value of the nitrogen atom IP.

Turning a Transition State into a Minimum—The Nature of the Bonding in Diplumbylene Compounds RPbPbR (R=H, Ar)

“…[20]. 2 P 3 4 S À excitation energy of PbH is the highest among the Group 14 hydrides EH ( Figure 5).…”

A Theoretical Study on Laser Cooling Feasibility of Group IVA Hydrides XH (X = Si, Ge, Sn, and Pb): The Role of Electronic State Crossing

“…Theoretically, in 1967 the first ab initio calculations on the SiH radical were performed with the Hartree-Fock method (Cade and Huo, 1967), in which the potential energy curve (PEC) of the ground-state was obtained. In 1983, the PECs of SiH were evaluated with the multi-reference double-excitation configuration interaction calculations (Lewerenz et al, 1983). In recent years, there are many calculations about spectroscopic constants of SiH (Ram et al, 1998;Kalemos et al, 2002;Shi et al, 2008Shi et al, , 2013Zhang et al, 2018).…”

Fourier Transform Emission Spectroscopy of theA2Δ–X2Π Transition of SiH and SiD

“…There are several calculations providing the estimates of dissociation energy of SiH between 3.0 to 3.35 eV. An upper limit of 3.06 eV has been obtained from the analysis of predissociation in the There are several theoretical predictions of the spectroscopic properties of the SiH radical (47)(48)(49)(50)(51)(52)(53)(54) (50) have applied the valence shell Hamiltonian method base on quasi-degenerate manybody perturbation theory to calculate the molecular properties including the valence state energies. Theoretical calculations have also been focused on the study of geometrical structures, force constants, and vibrational spectra and heats of formation of silane (SiH n ) and chlorinated silane molecules (SiH n Cl m ) (51-55).…”