Theoretical study on the transition properties of AlF

Abstract

Potential energy curves of the X1Σ+ and A1Π states of the AlF molecule are studied through the combination of the multi-reference configuration interaction (MRCI) approach and Davidson corrections (MRCI+Q). The AWCV5Z basis set is employed in the calculations. The transition dipole moments (TDMs) of the A1Π ↔ X1Σ+ transition are explored based on the AWCV5Z basis set and (4, 2, 2, 0) active space. The Schrödinger equation is solved via the LEVEL 8.2 program, and the vibrational levels and rotational constants of the X1Σ+ and A1Π states are calculated. It is shown that the AlF molecule has high diagonal Franck–Condon factors (f 00 = 0.9949 and f 11 = 0.9854) and large Einstein coefficients for the transition of A1Π (ν′ = 0) ↔ X1Σ+ (ν″ = 0). In addition, the radiative lifetimes of the vibrational levels are close to 10−9 s for the A1Π state. The line intensities of the A1Σ (ν′ = 4 – 15) ↔ X1Σ+ (ν″ = 0) transitions are also calculated. The calculated TDMs and transition probabilities in this work are credible and provide some guidance for the study of similar transitions, particularly for exploring interstellar space.

Ab initio spectroscopic studies of AlF and AlCl molecules

“…Our value of D e for A 1 Π state is in excellent agreement with the only result available in Ref. [23]. The MRCI + Q value of ω e x e = 5.70 cm −1 for A 1 Π state is very close to the experimental value of 5.99 cm −1 [31], while for a 3 Π (B 1 Σ) state, our value is larger by 1.53 cm −1 (1.17 cm −1 ) from the experimental data.…”

“…A very similar behaviour of PDM curve of this system has been reported in Ref. [23], though they have not mentioned about the usage of state -averaged procedure in their work. It has been observed that the values of PDMs are almost zero at the dissociation limit for all electronic states, which means that the molecule dissociates into its constituent neutral fragments.…”

“…The results for spectroscopic parameters obtained in this work compares well with the existing values. Except for ω e x e , the difference between our results for ground spectroscopic constants from that reported in the recent work by Zhang et al [23] is less than 1% at the same level of theory. Although, ω e x e is extracted from the PECs along with the other spectroscopic parameters via fitting, it is quite sensitive to the number of data points used for fitting.…”

“…The equilibrium bond lengths, rotational constants and components of dipole polarizabilities for the ground states of both the molecules have been reported by Woon and Herbst [24] at CCSD(T)/augmented correlation-consistent polarized valence triple zeta (aug-cc-pVTZ) level. Zhang et al [23] have studied the X 1 Σ and A 1 Π states at multi-reference configuration interaction (MRCI) level of theory using AWCV5Z basis set. The ro-vibrational transitions in the electronic ground states of AlF and AlCl molecular systems have been studied in Ref.…”

“…For example, the dissociation energies are not available for the excited states of AlF molecule except for A 1 Π state in Ref. [23]. The value of ω e y e , for the X 1 Σ state of AlF is not reported by any work, while for AlCl, ω e y e is reported only in Ref.…”