Infrared Fourier transform spectroscopy of XeH

Nonequilibrium vibrational excitation of OH radicals generated during multibubble cavitation in water

The sonoluminescence (SL) spectra of OH(A(2)Σ(+)) excited state produced during the sonolysis of water sparged with argon were measured and analyzed at various ultrasonic frequencies (20, 204, 362, 609, and 1057 kHz) in order to determine the intrabubble conditions created by multibubble cavitation. The relative populations of the OH(A(2)Σ(+)) v' = 1-4 vibrational states as well as the vibronic temperatures (T(v), T(e)) have been calculated after deconvolution of the SL spectra. The results of this study provide evidence for nonequilibrium plasma formation during sonolysis of water in the presence of argon. At low ultrasonic frequency (20 kHz), a weakly excited plasma with Brau vibrational distribution is formed (T(e) ~ 0.7 eV and T(v) ~ 5000 K). By contrast, at high-frequency ultrasound, the plasma inside the collapsing bubbles exhibits Treanor behavior typical for strong vibrational excitation. The T(e) and T(v) values increase with ultrasonic frequency, reaching T(e) ~ 1 eV and T(v) ~ 9800 K at 1057 kHz.

First spectroscopic studies of the B2Sigma+ --> X2Sigma+ system in the 12C17O+ molecule spectrum

The emission spectrum of the B2Sigma+ --> X2Sigma+ system in the 12C17O+ has been recorded at high resolution with conventional spectroscopic techniques. A graphite hollow cathode lamp filled with oxygen, enriched approximately 45% with the 17O2 isotope, has given strong spectra of hitherto unreported bands system of 12C17O+. Four bands, which form the 0-v('') (v('')=1 -4) progression, have been rotationally analysed with effective Hamiltonians of Brown [J. Mol. Spectrosc. 74 (1979) 294]. Next the rovibronic structure parameters, for the B2Sigma+ and X2Sigma+ states, have been determined from merge calculations. Finally, principal equilibrium molecular constants for the ground state: omegae=2186.032(26) cm(-1), omegae xe=14.7848(43) cm(-1), Be=1.927271(73) cm(-1) , alphae=1.8432(24) x 10(-2) cm(-1), De=6.018(26) x 10(-6) cm(-1), betae=1.11(92) x 10(-8) cm(-1) and the sigma(e)(B-->X)=45876.563(34) cm(-1) value of the 12CO17+ molecule have been derived for the first time in this investigation.

Experimental and Theoretical Study of the Electronic States and Spectra of TeH and TeLi

Gas-phase emission spectra of the hitherto unknown free radical TeLi have been measured in the NIR range with a Fourier-transform spectrometer. The emissions were observed from a fast flow system in which tellurium vapor in argon carrier gas was passed through a microwave discharge and mixed with lithium vapor in an observation tube. Two systems of blue-degraded bands were measured at high spectral resolution in the ranges 8000-9000 and 5700-6700 cm(-1) and vibrational and rotational analyses were performed. In order to aid in the analysis of the experimental data, a series of relativistic configuration interaction calculations has been carried out to obtain potential curves for the low-lying states of TeLi and the isovalent TeH and also electric dipole transition moments connecting them. As in the TeH system, the ground state of TeLi is found to be X(2)Pi(i), but with a remarkably smaller spin-orbit splitting. The TeLi calculations indicate a strongly bound A(2)Sigma(+) state, while in TeH the analogous state is computed to lie significantly higher at approximately 32 000 cm(-1), and it is strongly predissociated. Based on the theoretical analysis, the observed TeLi band systems are assigned to the transitions A(2)Sigma(+)(A1/2)-->X(1)(2)Pi(3/2)(X(1)3/2) and A(2)Sigma(+)(A1/2)-->X(2)(2)Pi(1/2)(X(2)1/2). Analysis of the spectra has yielded the molecular constants (in cm(-1)) X(1)(2)Pi(3/2):omega(e)=457.49(3), omega(e)x(e)=2.482(9), B(0)=0.408908(8); X(2)(2)Pi(1/2): T(e)=2353.44(3), omega(e)=456.28(4), omega(e)x(e)=2.635(8), B(0)=0.414954(8), p(0)=1.00637(4); A(2)Sigma(+): T(e)=8574.64(2), omega(e)=437.81(3), omega(e)x(e)=2.581(8), B(0)=0.423903(8), p(0)=-0.19915(2), where the numbers in parentheses are the standard deviations of the parameters. Comparison of the isovalent TeLi and TeH systems emphasizes that the difference in bonding character (ionic in TeLi vs covalent in TeH) is responsible for qualitative differences in the electronic spectra of these two molecules. Copyright 2001 Academic Press.

The Rotational Analysis of the A(2)Pi(r)-X(2)Sigma(+) Band System of MgBr

The A(2)Pi(r)-X(2)Sigma(+) emission spectrum of the magnesium monobromide radical, MgBr, has been recorded with a Fourier transform spectrometer modified to record double-sided interferograms. The emission spectra of the Deltav = -2, -1, 0, +1 bands were generated in a microwave discharge of a mixture of argon and vaporized MgBr(2). The Deltav = 0 and -1 bands were rotationally resolved, but the F(2) spin component (A(2)Pi(3/2)) in the (1, 1), (1, 2) and vibrational bands with v' > 1 were missing in our spectra because of a strong predissociation in the A state. The molecular constants in both electronic states were determined for the two bromine isotopomers. The r(0) bond length in the A state is about 2.327 Å, which is about 0.02 Å shorter than in the ground state. Franck-Condon factors were calculated from the Rydberg-Klein-Rees potentials, and they reproduce the observed relative intensities of the bandheads. An upper limit for the dissociation energy (D(0)(0)) was obtained as 26 268.4 cm(-1), based on the absence of the energy level with v = 1, A(2)Pi(3/2), J = 1.5 in our spectrum. Copyright 2000 Academic Press.

The Comet-Tail (A(2)Pi(i)-X(2)Sigma(+)) System of (12)C(16)O(+): A Reinvestigation

The emission spectrum of the comet-tail (A(2)Pi(i)-X(2)Sigma(+)) system of (12)C(16)O(+) produced in the cathode glow of a hollow-cathode discharge tube and photographed in the spectral region 3345-8500 Å at high resolution was reinvestigated. Detailed rotational analysis of 10 bands involving 5 vibrational levels v = 0 to 4 of each of the A and X states was carried out. Spin-splitting of the rotational levels was observed for the analyzed bands. The observed intensity distribution of the branches is found to be in good agreement with theoretical calculations. Molecular constants for both the A and X states were obtained from a global fit of the present data of the A-X system and the infrared and microwave data available from the literature for v = 0, 1, 2, 3, and 4 of state X, using effective Hamiltonian for the A(2)Pi state and matrix elements for both A and X states. The present work suggests that the A(2)Pi(i) state changes from Hund's case (a) at low J values to Hund's case (b) at high J values. Copyright 2000 Academic Press.

Fourier Transform Emission Spectroscopy of the A2Pi-X2Sigma+ Transition of BeD

The A2Pi-X2Sigma+ Deltav = 0 sequence of BeD was observed in the 19 500-20 800 cm-1 spectral region using a Fourier transform spectrometer. The emission spectrum was excited in a Be hollow cathode discharge lamp with a He/D2 gas mixture. The observed lines were assigned to the 0-0 to 6-6 bands. The Deltav = -1 sequence was too weak to be seen in our Fourier transform spectra. We therefore used a previously recorded but unpublished arc emission spectrum to identify the 0-1 to 5-6 Deltav = -1 bands. Consequently, all of the diagonal bands could be linked together and the vibrational intervals determined. The Deltav = 0 and Deltav = -1 data were fitted together in a global fit and effective constants derived. Using the information available from the study of the C2Sigma+-X2Sigma+ system [R. Colin, C. Drèze, and M. Steinhauer, Can. J. Phys. 61, 641 (1983)], the v = 8-12 vibrational levels of the ground state were added in a Dunham fit. A set of Dunham Y constants was determined for the X2Sigma+ state along with traditional equilibrium parameters for the A2Pi excited state. The equilibrium bond lengths were found to be 1.341742(5) Å for the ground state and 1.33309(4) Å for the excited state. A reanalysis of the previously published A2Pi-X2Sigma+ 0-0 to 3-3 Deltav = 0 bands of BeT [D. De Greef and R. Colin, J. Mol. Spectrosc. 53, 455-465 (1974)] was also performed. Copyright 1998 Academic Press.