The rotational spectrum of the NiI radical in the XΔ5∕22 and AΠ3∕22 states

Abstract

The millimeter- and submillimeter-wave spectra of the NiI radical in the X (2)Delta(5/2) and A (2)Pi(3/2) states were observed by a source-modulated microwave spectrometer. The NiI radical was generated by a dc glow discharge in the mixture of CH(3)I vapor and Ar gas through the sputtering reaction with a Ni cathode. Observed transition frequencies for each electronic state were independently analyzed using a polynomial energy expression based on Hund's case (c) approximation. The deperturbed rotational constants were also estimated by the perturbation analysis including interaction terms between the ground state and the lowest excited state.

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.…”

“…Also included in Table 1 are the previous experimental [15,16] and theoretical [17] x e and T e values. Note that previous experiments obtained vibrational information through the Table 1 Vibrational constants and term energies (in cm À1 ) of the five low-lying electronic states observed in the present work.…”

“…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].…”

Approximate theoretical model for the five electronic states (Ω=5/2, 3/2, 3/2, 1/2, 1/2) arising from the ground 3d9 configuration in nickel halide molecules and for rotational levels of the two Ω=1/2 states in that manifold

“…The change in viewpoint (i) was introduced in the hope that variation of empirical crystal-field parameters of NiX across the four halides (X = F, Cl, Br, I) will give additional chemical insight. The simplification (ii) was introduced because B NiX ( B NiH , so that many of the Luncoupling and S-uncoupling interactions that must be treated by exact diagonalization in NiH [27], can be treated by second-order perturbation theory in the nickel halides [16,17,21]. Note also that perturbations arising from Dv -0 interactions among the 3d 9 electronic states [27] are missing from these small matrices.…”

“…Examples of such studies (with rotational resolution) are: NiF [1][2][3][4][5][6][7], NiCl [8][9][10][11][12][13][14], NiBr [15][16][17], NiI [18][19][20][21], and NiH [22][23][24][25][26]. The electronic states of these and related molecules have also been studied theoretically [27][28][29][30][31][32].…”