The Na 7Li 3 1Σ+(C) and 1 1Π(B) electronic states through collision energy transfer

Abstract

The NaLi 3 1Σ+(C)→2 1Σ+(A) electronic transition has been observed in the infrared region after laser excitation of the 1 1Π(B) electronic state and subsequent collisional energy transfer between the 1 1Π(B) and 3 1Σ+(C) electronic states. The spectra were recorded at high resolution by Fourier-transform spectroscopy. Thirteen vibrational bands were analyzed, providing detailed information for the 2 1Σ+(A) (v=0,...,4) and 3 1Σ+(C) (v=5,...,13) vibrational levels. Rotational perturbations have been observed in the spectra. The nearly 1200 observed lines belonging to 1 1Π(B)→2 1Σ+(A) and 3 1Σ+(C)→2 1Σ+(A) transitions have been assigned and reduced to molecular constants in a linear least-squares fit. Perturbations observed in the upper electronic states have been reduced using a nonlinear least-squares fit to a 1Σ∼1Π effective Hamiltonian matrix model. Deperturbed molecular constants and perturbation parameters are obtained for the 1 1Π(B) electronic state (v=0,...,6) and the 3 1Σ+(C) electronic state (v=5,...,13) levels. Propensity rules concerning the energy gaps and the conservation of angular momentum, during the energy transfer, are inferred from the intensity distributions of anomalous lines.