G. Wannous

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

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 74Ge2 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 3Σg− state to a 3Σu− excited state. The bond lengths derived from the rotational constants are r0″=2.3680(1) A and re′=2.5244(18) A, an ∼0.16 A 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 ...

Spectroscopy and predissociation of the 3A2 electronic state of ozone 16O3 and 18O3 by high resolution Fourier transform spectrometry

A high resolution Fourier transform spectrometry analysis of the rotational structure of the 2(0)1 absorption bands of the 3A2<--X1A1 Wulf transition for the isotopomers 16O3 and 18O3 of the ozone molecule is presented. These bands are very intense compared to the 0(0)0 bands but the predissociation is so strong that the main sub-bands appear as continuous contours. Isolated lines and band contour methods are used together to analyse these two rovibrational bands. The lines corresponding to the F2 component are generally the most intense and isolated. Our data sets for the (0 1 0) level of the 3A2 state are limited to about 102 weakly or unperturbed rotational lines for the 2(0)1 of 16O3 in the range 9620-10,140 cm(-1) and 123 weakly or unperturbed rotational lines for the same band of 18O3. Using for each of them the well-defined ground state parameters, we obtained a standard deviation of about 0.035 cm(-1) in the fit to the lines for 16O3 and 0.027 cm(-1) in the case of 18O3. The rotational constants A, B and C, the three rotational distortion terms deltaK, deltaJK and deltaJ, the spin-rotation constants a0, a and b have been successfully calculated for 16O3 and 18O3 while the spin-spin constants were fixed to their respective values obtained for the origin bands. As is the case for the 0(0)0 band, we have a partial agreement with the isotopic laws for the rotational constants. The geometrical parameters of the (0 1 0) level of 3A2 state for the two isotopomers are close, r = 1.357 A, theta = 100.7 degrees for 18O3 and r = 1.352 A and theta = 100.0 degrees for 16O3. The origin of the 2(0)1 band of 18O3 is red shifted by 7.06(4) cm(-1) with respect to 16O3 2(0)1 band and the two bending mode quanta are, respectively, 528.99(9) and 501.34(7) cm(-1). A preliminary qualitative analysis of the predissociation is given in the particular case of the F2 spin component of 16O3 for 0(0)0 and 2(0)1 bands by the measurement of shifts of positions of some rovibrational levels and the evolution of predissociation broadenings in (Q)Q2 branches. We justify the existence of perturbations in the rovibrational levels of 3A2 state through different interaction types: with the dissociation continuum of the same electronic state or with high vibrational repulsive or weakly bound levels of the ground state.

ELECTRONIC STATES OF SCANDIUM MONOIODIDE

The many electronic transitions observed in high-resolution spectra of the fluorescence of scandium monoiodide following excitation by Ar+ and Kr+ laser lines have been extensively analyzed. Equilibrium vibrational and rotational constants are obtained for the six lowest electronic states. Spin-orbit constants in a3Delta and b3Pi are also determined. The laser-excited levels are regrouped into two electronic states, of 1Pi and 3Pi symmetries, for which molecular constants are derived. Copyright 1997 Academic Press. Copyright 1997Academic Press

Electronic states of Bi2

Laser-induced fluorescence and thermal emission spectra of Bi2 have been recorded at high resolution by Fourier transform spectrometry. Extensive analyses, involving the assignment of more than 20 000 lines, have been made of transitions involving the states X 0+ g, a lu(3Σ+ u), A 0+ u(3Σ- u) and E lg. The electronic states of Bi2 are reviewed, and comparison is made with the results of ab initio calculations.

Contribution to the analysis of the predissociated rovibronic structure of the symmetric isotopomers and of ozone near 10,400 cm−1: and

The absorption spectrum of ozone was recorded at low temperatures (down to -135 degrees C) by high resolution Fourier transform spectrometry and intra cavity laser absorption spectroscopy (ICLAS) near 10,400 cm-1. A preliminary analysis of the rotational structure of the absorption spectra of 16O3 and 18O3 shows that this spectral region corresponds to a superposition of two different electronic transitions, one with a very broad rotational structure, showing for the first time the asymmetric stretching frequency mode nu3 of the electronic state 3A2, the other formed by a completely diffuse band, probably the 2(1)(0) band of a new transition due to the triplet electronic state 3B2. Predissociation effects induce large broadening of the rotational lines for the transition centered at 10,473 cm-1 identified as the 3(2)(0) band of the 3A2 <-- X1A1 electronic transition. The rotational structure cannot be analyzed directly but instead the band contour method was used to confirm the symmetry of the transition and to estimate the spectroscopic constants for the 16O isotopomer. The origin of the band is at 10,473 +/- 3 cm-1 and the value of the 16O3(3A2) antisymmetric stretching frequency mode is equal to 460 +/- 2 cm-1. We believe that the diffuse band is due to the 3B2 state and is located at about 10,363 +/- 3 cm-1 for 16O3 and 10,354 +/- 3 cm-1 for 18O3. The isotopic rules confirm the different results obtained for 18O3 and 16O3.

Electronic states of the Bi2 molecule

Abstract The thermal emission spectrum of Bi2 in the region 3500 to 9000 cm−1 has been recorded by Fourier transform spectrometry, and laser-induced fluorescence spectra of Bi2, excited by lines of an argon-ion laser, have also been recorded. The dense thermal emission spectrum consists predominantly, if not entirely, of lines of a system a1u (3Σ+u)-XO+g. The state a1u, is the lower state of a system observed in LIF and originally labelled EB. Vibrational and rotational constants are derived for the states involved. Measurement of the small Ω-doubling in alu allows an estimate of the (O−u-1u) separation in a 3Σ+u to be made: it is 4540 cm−1.

Electronic transitions of ScI: preliminary results from high resolution LIF spectroscopy

Electronic transitions of ScI observed in high resolution spectra of the fluorescence induced by laser line excitations are analysed. Preliminary values of molecular constants are obtained for states of the lowest electronic configuration, , , , , , and for the laser-excited state.