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

Abstract

High-resolution laser-induced fluorescence spectrum of a jet-cooled NiI molecule has been recorded in the near infrared and visible regions. The NiI molecule was produced by reacting laser-ablated nickel atom and methyl iodide (CH 3 I). Three electronic states have been identified that include the X 2 ⌬ 5/2 and two low-lying ͓13.9͔ 2 ⌸ 3/2 and ͓14.6͔ 2 ⌬ 5/2 excited states. Molecular transition bands (vЈ,0) of the ͓13.9͔ 2 ⌸ 3/2 ϪX 2 ⌬ 5/2 system with vЈϭ0, 4-9, and the (vЈ,0) bands of the ͓14.6͔ 2 ⌬ 5/2 ϪX 2 ⌬ 5/2 system with vЈϭ0-6 were observed and analyzed. Spectra of isotopic molecules confirmed the assignment of vibrational quantum number of the observed bands. Least squares fit of rotational transition lines yielded accurate molecular constants for the states studied. The bond length r 0 measured for the X 2 ⌬ 5/2 is 2.3479 Å and the equilibrium bond length, r e , for the ͓13.9͔ 2 ⌸ 3/2 and ͓14.6͔ 2 ⌬ 5/2 are, respectively, 2.4834 and 2.5081 Å. With the use of a molecular orbital energy level diagram, we have examined the electronic configurations that give rise to the X 2 ⌸ 3/2 ground state for NiF, NiCl, and NiBr, but the X 2 ⌬ 5/2 state for NiI. This work represents the first spectroscopic study of the NiI molecule.

Fourier transform spectroscopy of NiCl: identification of a [9.1] state

“…2. For comparison, the known states of the nickel halides [1][2][3][4][5][6][13][14][15] are presented in Fig. 3.…”

Laser induced fluorescence spectroscopy of boron carbide

“…Our laser induced fluorescence (LIF) spectrometer and the laser ablation/reaction free jet expansion system were described elsewhere [13,14], only experimental details pertinent to the recording of the BC spectrum are given here. BC molecules were generated by the reaction of a gas mixture of 0.5% B 2 H 6 and 3% CH 4 in argon in the presence of laser ablated magnesium (Mg) atoms.…”

Single vibronic level emission spectroscopy of the low-lying electronic states of NiI

“…It is possible to identify five distinct vibrational progressions. In addition to the X 2 D 5=2 and A 2 P 3=2 states characterized in previous work [14][15][16], three additional electronic states have been identified. Based on the theoretical work of Zou and Liu [17], these are assigned as the A 2 P 1=2 , X 2 D 3=2 , and B 2 R þ 1=2 states.…”

“…Excited state symmetries have been tentatively assigned based on preliminary rotational simulations [21] and analysis of the single vibronic level emission spectra. In the following discussion, these states will be identified using the nomenclature adopted by Tam et al [14,15] and vibrational analysis of these band systems will be discussed in a future publication.…”

“…The limited experimental work has focused on the two lowest energy electronic states, observed using laser-induced fluorescence (LIF) [14,15] and microwave spectroscopy [16]. Indeed, the ground state has been unambiguously identified only in the last decade, in the high resolution studies of Cheung and co-workers [14,15]. Assignment of the ground state in that work as 2 D 5/2 is consistent with NiH, but differs from the lighter monohalide analogues, which feature a 2 P 3/2 ground state.…”