Eur. Phys. J. D (2014) 68: 123
https://doi.org/10.1140/epjd/e2014-40632-7

Regular Article

Extensive spectroscopic calculations on 12 low-lying electronic states of AlN molecule including transition properties

¹ College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007, P.R. China
² College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, P.R. China

^a e-mail: scattering@sina.com.cn

Received: 15 October 2013
Received in final form: 17 March 2014
Published online: 15 May 2014

Abstract

Using the CASSCF method followed by the internally contracted MRCI approach in combination with the correlation-consistent basis sets, the potential energy curves (PECs) are calculated for the X³Π, A³Σ^-, B³Σ⁺, C³Π, E³Δ, a¹Σ⁺, b¹Π, c¹Δ, d¹Σ⁺, e¹Π, 2³Σ⁻ and 3³Σ⁻ electronic states of AlN molecule for internuclear separations from 0.1 to 1.0 nm. All the electronic states correlate to the three dissociation channels, Al(²P_u) + N(⁴S_u), Al(²P_u) + N(²D_u) and Al(²P_u) + N(²P_u). Of these 12 electronic states, only the 2³Σ⁻ possesses the double well. The PECs determined by the internally contracted MRCI approach are corrected for size-extensivity errors by means of the Davidson correction. The convergent behavior of present calculations is observed with respect to the basis set and level of theory. The effect of core-valence correlation and scalar relativistic corrections on the spectroscopic parameters is discussed. Scalar relativistic correction calculations are performed by the third-order Douglas-Kroll Hamiltonian approximation at the level of cc-pVTZ basis set. Core-valence correlation corrections are included with a cc-pCVTZ basis set. All the PECs are extrapolated to the complete basis set limit. The spectroscopic parameters are evaluated by fitting the first ten vibrational levels when available, which are obtained by solving the ro-vibrational Schrödinger equation with the Numerov’s method. The spectroscopic parameters are compared with those reported in the literature. Excellent agreement is found between the present results and the measurements. Analyses show that the spectroscopic parameters reported in this paper can be expected to be reliably predicted ones. The Franck-Condon factors and radiative lifetimes of the transitions from the A³Σ⁻, B³Σ⁺, C³Π, a¹Σ⁺ and b¹Π electronic states to the ground state are calculated for several low vibrational levels, and some necessary discussion has been made.