Laser spectroscopy of NiBr: Ground and low-lying electronic states

Abstract

Four electronic states of NiBr have been studied using the technique of laser vaporization/reaction with supersonic cooling and laser induced fluorescence (LIF) spectroscopy. NiBr molecules were produced by reacting laser ablated nickel atoms and ethyl bromide (C2H5Br). High resolution LIF spectrum between 724 and 810 nm was recorded, which consists of the (2,0), (1,0), and (0,0) bands of the [13.2] Π3/22–X 2Π3/2 system and the [13.2] Π3/22–A 2Δ5/2 system, and also the (v,0) with v=0–4 bands of the [12.6] Σ+2–X 2Π3/2 system. Spectra of four isotopic molecules: Ni58Br79, Ni58Br81, Ni60Br79, and Ni60Br81 were observed and analyzed. Least squares fit of rotationally resolved transition lines yielded accurate molecular constants for the X 2Π3/2, A 2Δ5/2, [12.6] Σ+2, and [13.2] Π3/22 electronic states of NiBr. The bond length, r0, measured for the X 2Π3/2 and A 2Δ5/2 states is 2.196 28 and 2.164 45 Å, respectively. A molecular orbital diagram has been constructed to explain the four observed electronic states. This work represents the first high-resolution spectroscopic study of NiBr.