MRCI+Q study of the low-lying electronic states of CdF including spin–orbit coupling

Abstract

CdF molecule, which plays an important role in a great variety of research fields, has long been subject to numerous researchers. Due to the unstable nature and heavy atom Cd containing in the CdF molecule, electronic states of the molecule have not been well studied. In this paper, high accurate ab initio calculations on the CdF molecule have been performed at the multi-reference configuration interaction level including Davidson correction (MRCI + Q). Adiabatic potential energy curves (PECs) of the 14 low-lying Λ-S states correlating with the two lowest dissociation limits Cd( 1 S g ) + F( 2 P u ) and Cd( 3 P u ) + F( 2 P u ) have been constructed. For the bound Λ-S and Ω states, the dominant electronic configurations and spectroscopic constants are obtained，and the calculated spectroscopic constants of bound states are consistent with previous experimental results. The dipole moments (DMs) of 2 Σ + and 2 Π are determined, and the spin-orbit (SO) matrix elements between each pair of X 2 Σ + , 2 2 Σ + , 1 2 Π, and 2 2 Π are obtained. The results indicate that the sudden changes of DMs and SO matrix elements arise from the variation of the electronic configurations around the avoided crossing region. Moreover, the Franck-Condon factors (FCFs), the transition dipole moments (TDMs), and radiative lifetimes of low-lying states-the ground state X 2 Σ + are determined. Finally, the transitional properties of 2 2 Π-X 2 Σ + and 2 2 Σ + -X 2 Σ + are studied. Based on our computed spectroscopic information of CdF, the feasibility and challenge for laser cooling of CdF molecule are discussed.

Theoretical electronic structure of the cadmium monohalide molecules CdX (X = F, Cl, Br, I)

“…(1) shows that the electronic ground state of CdF is the X 2 Σ + state with R e = 2.042 Å. For the ground state, the calculated equilibrium bond length R e =2.042 Å is in very good agreement with the previously reported values theoretically [25][26][27][28] where the relative difference varies between (0.17%)≤∆R e /R e ≤(4.0%). Our calculated vibrational harmonic frequency ω e = 479.0 cm -1 reveals a good agreement with the experimental value of 535 cm -122 and with those computed theoretically where the relative difference ranges between (0.8%)≤∆ω e /ω e ≤(12.7%).…”

“…Our calculated vibrational harmonic frequency ω e = 479.0 cm -1 reveals a good agreement with the experimental value of 535 cm -122 and with those computed theoretically where the relative difference ranges between (0.8%)≤∆ω e /ω e ≤(12.7%). [25][26][27][28] The rotational constant B e = 0.2484 cm -1 calculated in the present work at the MRCI+Q level varies from the theoretical value B e = 0.2704 cm -128 by 0.022 cm -1 . Our computed dipole moment µ = 4.0051 D shows a good agreement when compared to the theoretical results 27 where the relative differences is 2.5%.…”

“…Our computed dipole moment µ = 4.0051 D shows a good agreement when compared to the theoretical results 27 where the relative differences is 2.5%. However, a value of 2.2113 D is determined by Zhao et al 28 The (2) 2 Σ + state presents a deep minimum around R = 3.272 Å, resulting from the interaction with the X 2 Σ + ground state which corresponds to a transition energy of 25928.21cm -1 with respect to the minimum of X 2 Σ + state. However, the (3) 2 Σ + state shows a shallow minimum around R = 1.94Å.…”

“…Our spectroscopic constants of the (2) 2 Σ + state are compared to those given in literature experimentally 22 and theoretically. 28 Huber and Herzberg 22 summarized the values of T e and ω e as 34200 cm -1 and 535 cm -1 respectively. Our computed values of T e =25928.21 cm -1 and ω e = 202.48 cm -1 are quite different from those indicated experimentally.…”

“…26 In 2007, Cheng et al 27 calculated the equilibrium internuclear distance, the vibrational harmonic frequency, the dissociation energy, the ionization potential (IP), the electron affinity (EA), and the dipole moment for the ground state X 2 Σ + of the title molecules in both neutral and charged molecules via the density functional method B3LYP. Recently, the more extensive calculations have been conducted by Zhao et al 28 at the multi-reference configuration interaction level including Davidson correction (MRCI+Q). They calculated the spectroscopic constants for 9 low-lying Λ-S electronic states including the ground state; one can notice the absence of the comparison of their data with those obtained by Cheng et al 22 Regarding the CdCl molecule, the first experimental study was reported by Walter and Barratt.…”