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The oxides TiO, CrO, and CoO, formed by reaction of the laser-ablated metal toms and O2 in excess argon during condensation at 10 K are laser desorbed/ionized from solid argon with 308 nm radiation for observation by TOF mass spectrometry. The laser desorption/ionoztion process in cryogenic experiments with low ionization energy subject atoms and molecules is assisted by the organic acid and bromobenzene chromopores.

This review takes the reader from the rich and diverse dynamics of ArI(sub)2 molecule to the complex phenomena of van der Waals cluster dynamics. Data on combinations of noble gas atoms and halogen molecules with reference to sequential relaxation pathways and intramolecular vibrational relaxation limit are presented.

The potential energy surface of He2Ne+ has been reinvestigated using a combination of ab initio and diatomics-in-molecule (DIM) calculations. In contrast to the reports of two recent studies the ion is found to have an asymmetric linear He–Ne–He structure, with no barrier to formation from the separated atoms on the ground-state surface. The He–Ne+ bond lengths at the potential minimum are 1.51 and 1.81 Å, and the total bonding energy is 0.717 eV. Comparing the He2Ne+ energy to that of HeNe+, the bonding energy for the second helium atom is 0.06 eV, about 10% of that of the first He atom. The saddle point between the two equivalent minima is a symmetric structure, 0.0074 eV above the potential minimum. A symmetric geometry becomes the overall potential minimum if the 2s hole on the Ne is excluded from the reference states of a multireference configuration interaction calculation. A DIM potential was created for the HenNe+ family of ions. The DIM potential is consistent with the asymmetric He2Ne+ ion serving as a core; it predicts a slightly more asymmetric geometry than the ab initio results. Additional helium atoms form five-membered rings around the bonds of the core ion to fill the first shell and then add to the ends of the cluster. The asymmetric core ion and the highly compact structure help to account for the lack of apparent shell structure in the mass spectrometry of HenNe+ clusters. Finally, we recommend that the value De=0.63±0.04 eV be adopted for the ground state of HeNe+. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An inexpensive and portable ammonia monitoring system based on near-infrared GaAs-type diode lasers is described. The minimum detectable ammonia concentration is 2 parts in 10 to the sixth power at 100 Torr (with 1-s response time and 1-m absorption path length).

Studies a three-dimensional potential energy surface for the noble gas dihalogen complex He+Cl[sub 2]. Calculation of excitation spectra; Predissociation lifetimes; Product state distributions; Excited state vibrational level.

Describes a combined experimental-theoretical study of the vibrational predissociation and product rotational distributions for high vibrational levels of He[sup 79]Br[sub 2] molecules. Pump-probe method used in the study; Quantum-mechanical calculations; Agreement between the results of the experiment and theory.

Infrared laser kinetic spectroscopy was extended to the study of formation and decomposition processes in a hollow cathode discharge. The processes responsible for the disappearance of the CN radical in different vibrational states (v=0–7) were investigated. From the time evolution of the signal, information on the reaction rates of vibrationally excited CN molecules with C2N2 and on their vibrational relaxation could be obtained. The measured first order reaction rate constants lie between 350–800 s-1 and the rate constants for the deactivation, which is thought to be due to V–V relaxation in collisions with C2N2, between 520–900 s-1 for the v=0–7 states of CN. [ABSTRACT FROM AUTHOR]

Reports on calculations of the interaction of helium with the B (supra 3)II[sub 0u] state of Cl[sub 2] as a function of the Cl[sub 2] internuclear separation. Calculation of vibrational predissociation rates, excitation spectra and rotational product distributions; Center potential energy functions fitted to the modified perturbation points.

The structure, dissociation dynamics, and intermolecular potential energy surfaces of the He79Br2 van der Waals molecule have been studied using high resolution, two color, pump–probe laser induced fluorescence spectroscopy and three dimensional quantum mechanical calculations. A conical nozzle produces higher centerline cluster densities than a standard nozzle, and allows data collection further downstream from the nozzle. This yields improved signal to noise ratios and lower Doppler widths. He79Br2 is found to have a T-shaped average geometry with He to Br2 center-of-mass distances of 3.98 Å and 4.11 Å for the X and B states, respectively, somewhat longer than previously reported. Spectra were also obtained for excitation to excited bending levels of the van der Waals coordinate. However, these spectra have yet to be rotationally assigned. Vibrational predissociation line widths for the B state of He79Br2 have been measured for three new vibrational levels and range from 0.036 cm-1 for B, v′=8 to 0.062 cm-1 for B, v′=12.These values are somewhat larger than was expected based on previous HeBr2 linewidth measurements for higher vibrational levels. Forms for the potential energy surface that have previously been used to simulate the spectra of HeCl2 have been applied to the HeBr2 data. For the HeBr2 X state, two potentials are tested. First, a slightly anisotropic, one center Morse–Spline–van der Waals potential with angle dependent parameters is used. Second a much more anisotropic potential obtained from ab initio calculations is tested. The more anisotropic potential produces a significantly better fit to the data. The B state potential is constructed using Morse atom–atom potentials for the short range part of the He–Br interaction. This simple potential is sufficient to fit the main excitation band, but does not yield a fit to spectra involving vibrationally excited van der Waals modes. ©... [ABSTRACT FROM AUTHOR]

The potential energy surface of He2Ne+ has been reinvestigated using a combination of ab initio and diatomics-in-molecule (DIM) calculations. In contrast to the reports of two recent studies the ion is found to have an asymmetric linear He-Ne-He structure, with no barrier to formation from the separated atoms on the ground-state surface. The He-Ne+ bond lengths at the potential minimum are 1.51 and 1.81 A, and the total bonding energy is 0.717 eV. Comparing the He2Ne+ energy to that of HeNe+, the bonding energy for the second helium atom is 0.06 eV, about 10% of that of the first He atom. The saddle point between the two equivalent minima is a symmetric structure, 0.0074 eV above the potential minimum. A symmetric geometry becomes the overall potential minimum if the 2s hole on the Ne is excluded from the reference states of a multireference configuration interaction calculation. A DIM potential was created for the HenNe+ family of ions. The DIM potential is consistent with the asymmetric He2Ne+ ion serving as a core; it predicts a slightly more asymmetric geometry than the ab initio results. Additional helium atoms form five-membered rings around the bonds of the core ion to fill the first shell and then add to the ends of the cluster. The asymmetric core ion and the highly compact structure help to account for the lack of apparent shell structure in the mass spectrometry of HenNe+ clusters. Finally, we recommend that the value De=0.63+/-0.04 eV be adopted for the ground state of HeNe+., ((c) 2004 American Institute of Physics)