The low-lying electronic states of CrF and CrCl: Analysis of the A 6Σ+→X 6Σ+ system of CrCl

Abstract

A high-resolution near infrared spectrum of the CrCl radical has been recorded in thermal emission with Fourier transform techniques in the interval from 6 900 cm−1 to 11 500 cm−1. Two dominating band systems have been found in this region; (1) The A 6Σ+→X 6Σ+ system, analyzed in the present work, consisting of the (0,0), (0,1), (1,0), (2,0), and (3,0) bands, the (0,0) band being located at around 9450 cm−1; (2) the B 6Π→X 6Σ+ system, with a band interpreted as (0,0), located between 8700 cm−1 and 9000 cm−1, overlapping the (0,1) band of the A 6Σ→X 6Σ+ system. A rotational analysis of the A 6Σ+→X 6Σ+ system has been carried out, and the following principal parameters (cm−1) have been derived: X 6Σ+: ωe=396.6621, Be=0.167 587 3, De=1.1835⋅10−7; A 6Σ+: ωe=379.39, Be=0.156 51. Local perturbations in the A 6Σ+ (v=0,1) levels have been attributed to interactions with the B 6Π (v=1,2) levels. In the present work, we have constrained the investigations on the B 6Π→X 6Σ+ system to the verification that the lower state is indeed X 6Σ+. This verification has been achieved through successful matchings of branches in that system to known combination differences of X 6Σ+. The assignment of the upper state as B 6Π is based on the characteristic appearance of the band. Ligand field and density functional calculations have been performed on CrF and CrCl. The results from these calculations indicate that the approximate structure of the B 6Π and 1 6Δ excited states of CrF and CrCl is Cr+[3d44s(6D)]X−, while for the X 6Σ+ ground state in both molecules it is Cr+[3d44s(6D)∼3d5(6S)]X−. A combined DFT/LFT treatment has been carried out on the Cr+ 3d5and 3d44s configurations of both molecules in order to calculate the location of the A 6Σ+ state and of a number of low-lying states in the quartet manifold.

The low-lying electronic states of FeO+: Rotational analysis of the resonance enhanced photodissociation spectra of the Π7/26←X 6Σ+ system

“…The results are listed in Tables V and VI, respectively. The results of the TD-DFT calculations performed on CrF are slightly worse than those obtained by Harrison et al 32 at the RCCSD͑T͒ level of theory and slightly better than the values obtained by Bencheikh et al 28 tively. The deviation in the calculated excitation energies is consistent with the 1500 cm Ϫ1 deviation obtained by Borowski and Broclawik 26 in the prediction of excited states of VO and MoO using TD-DFT.…”

Rotational analysis of the $3_0^1 $31 band of the $\tilde A{}^6\Sigma ^ + \leftarrow \tilde X{}^6\Sigma ^ + $Ã6Σ+←X̃6Σ+ system of CrCCH

“…The expected ground electronic state of CrCCH,X 6 + , is strongly supported by elementary considerations of chemical bonding, by computational chemistry, and by comparison to the closely related chemical species CrH, 39,40 CrF, 38,41,42 CrCl, 43,44 and CrCN, 45 all of which have 6 + ground states. Accordingly, we consider no other possibilities for the ground state symmetry.…”

“…47 In both CrF and CrCl, the B 6 state corresponds to a Cr + ion in its excited 3d 4 4s 1 , 6 D term interacting with a closed shell halide ion, with the Cr + electrons organized in a dδ 2 dπ 1 dσ 1 sσ 1 , 6 configuration. 44,48 In such a configuration, the spin-orbit constant, A, may be calculated using semi-empirical methods to be 1/5ζ 3d (Cr), which is expected to fall in the range 45-49 cm −1 . 49 Values similar to these would be expected in theB 6 state of CrCCH.…”

Theoretical study with vibration–rotation and dipole moment calculations of quartet states of the CrCl molecule

“…In literature, there are only few theoretical results for the quartet states (1) 4 R þ , (1) 4 P, and (1) 4 D of the CrCl molecule. The spectroscopic constants of these states have been calculated by Bencheikh et al [4], Harrison et al [2], and Koivisto et al [1] by using the ligand field and density functional techniques, variety of ab initio method and MRCI, and spin-orbit-configuration interaction calculation, respectively.…”

“…The spectroscopic constants of these states have been calculated by Bencheikh et al [4], Harrison et al [2], and Koivisto et al [1] by using the ligand field and density functional techniques, variety of ab initio method and MRCI, and spin-orbit-configuration interaction calculation, respectively. They calculated the electronic energy with respect to the minimum energy of the ground state T e , the internuclear distance r e , the harmonic frequency x e, and the permanent dipole moments l. In the present work, 10 low-lying quartet electronic states of CrCl molecule have been investigated by using the ab initio method.…”