Exploring the Bermuda triangle of homonuclear diatomic spectroscopy: The electronic spectrum and structure of Ge2

Abstract

The optical spectrum of jet-cooled Ge2 has been observed for the first time. Laser-induced fluorescence (LIF) and wavelength resolved emission spectra were recorded using the pulsed discharge technique with a tetramethylgermane precursor. Analysis of the spectra yielded the vibrational constants ωe″=287.9(47), ωexe″=0.81(55), ωeye″=0.0037(18), ωe′=189.0(15), ωexe′=6.41(30), and Te′=20 610.8(16) cm−1. High-resolution rotationally resolved spectra of several bands of Ge274 show two strong P and R branches and two very weak Q branches. We have assigned the band system as a Hund’s case (c) Ω′=1−Ω″=1 transition from the ground Σg−3 state to a Σu−3 excited state. The bond lengths derived from the rotational constants are r0″=2.3680(1) Å and re′=2.5244(18) Å, an ∼0.16 Å increase on electronic excitation. Arguments are presented for assigning the transition to a σg2πu2→σg2πuπg electron promotion, although the observed increase in the bond length is much less than predicted by previous ab initio calculations. The absence of the 0u+–0g+ component in the spectra has been attributed to an excited state predissociation.

Theoretical studies on singlet and triplet states of Ge2

“…Overall there is good agreement between this study and the literature values. The experimental r e for the GS, 2.37 Å [12], is smaller than any of the calculated values, all lying between 2.42 and 2.45 Å . The observed vibrational frequency of 288 cm À1 , however, agrees quite well with the calculated values of this work and of [14].…”

“…Of particular interest is 1 3 AE À u , which has been postulated to be the higher-energy state observed in the emission spectrum of [12]. Both T e and !…”

“…In a recent experimental paper by Hostutler et al [12], laser-induced fluorescence (LIF) and emission spectra of Ge 2 were reported. The observed band system was assigned as a Hund's case (c) ¼ 1 !…”

Systematically Convergent Correlation Consistent Basis Sets for Molecular Core−Valence Correlation Effects: The Third-Row Atoms Gallium through Krypton

“…This bond length contraction is beneficial as quintuple-level geometries are now within 0.01 Å of the experimental r 0 value obtained by Clouthier and co-workers. 93 Employing our ab initio value of the vibration-rotation interaction constant, R e , of 8.1 MHz yields an ab initio r 0 that is slightly longer than r e by 0.002 Å, which does result in better agreement with experiment. However, the final CCSD(T) r 0 is shorter than that of experiment by about 0.004 Å. Harmonic frequencies are in good agreement and slightly overshoot the experimental value by 2.5-3.0 cm -1 .…”

“…However, the final CCSD(T) r 0 is shorter than that of experiment by about 0.004 Å. Harmonic frequencies are in good agreement and slightly overshoot the experimental value by 2.5-3.0 cm -1 . On the basis of the experimental atomic SO splitting, as well as the molecular SO levels determined by Clouthier and coworkers, 93 can be shifted to a non-SO D 0 value of 67.7 kcal mol -1 . When corrected for ZPE effects, the aCV5Z-DK/awCV5Z-DK D 0 values are in good agreement.…”