FTIR spectra of NaTe and KTe and ab initio calculations of the electronic structure of these molecules

Abstract

Gas phase emission spectra of the hitherto unknown radicals NaTe and KTe have been measured in the NIR range with a Fourier-transform spectrometer. The emissions were observed from a fast-flow system in which tellurium vapor in argon carrier gas was passed through a microwave discharge and mixed with sodium or potassium vapor in an observation tube. Excitation of the radicals mostly occurred by near-resonant E-E energy exchange from added metastable oxygen O2(a1Δg). Like for the previously studied LiTe molecule, for both radicals two systems of blue-degraded bands were measured in the range 4500–8500 cm−1. They were assigned to the transitions A2Σ+(A1/2) → X12Π3/2(X13/2) and A2Σ+(A1/2) → X22Π 1/2(X21/2). For all four subsystems vibrational analyses were performed which yielded ground state splittings of 2265.39(13) cm−1 (NaTe) and 1544.19(11) cm−1 (KTe) as well as A2Σ+ state energies of 7935.98(9) cm−1 (NaTe) and 6404.71(11) cm−1 (KTe) and vibrational constants of the X13/2, X21/2 and A1/2 states of both molecules. The 0-0 bands of both sub-transitions of NaTe were measured at high spectral resolution and rotationally analyzed.In order to aid in the analysis of the experimental data, a series of relativistic configuration interaction calculations has been carried out to obtain potential curves for the low-lying states of NaTe and KTe and also electric dipole transition moments connecting them.