ABSTRACT
The stable structures and low temperature thermodynamics of cationic helium clusters are investigated theoretically using a diatomics-in-molecules model for the potential energy surfaces and a computational framework in which both electronic and nuclear degrees of freedom are treated on a quantum mechanical footing. While the charge is generally carried by two atoms, vibrational delocalization significantly spreads out the charge over multiple isomers for clusters containing five or more helium atoms. Our calculations indicate that large clusters are essentially fluid with a well-defined solvation shell around the charged core.
ABSTRACT
The Van der Waals complex Li...FCH3 has been formed in a crossed molecular beam apparatus. The transition state (TS) for the reaction Li*(2p 2P) + FCH3-->LiF + CH3 was accessed at various configurations by laser-excitation of the Li...FCH3 complex by tunable visible radiation, lambda 1. Photoinduced depletion of the complex by excitation to this TS was found to occur across a broad range of lambda 1 from 570 to 850 nm. This 'action spectrum' consisted of two broad regions located to either side of the atomic transition line of Li (2p 2P<--2s 2S). The first region, between 700 and 850 nm, was dominated by sharp maxima in the depletion intensity. A broad peak with weakly-resolved structure characterized the second region, between 570 and 680 nm. These findings were interpreted by means of high-level ab initio calculations of the potential-energy surfaces in the TS region. The peaks in the photodepletion spectrum were assigned to specific electronic transitions, their shapes and intensities being explained in terms of calculated transition-dipole moments and rovibrational wavefunctions.
ABSTRACT
New high-level ab initio calculations for ArI and ArI(2) are reported and compared with experimental data. For the directly calculated potential energy surface (PES), the bond dissociation energies D(0) values for both linear (L) and T-shaped (T) conformers of Ar-I(2) are found to be significantly larger (D(0)(L)≈197 and D0 (T)≈181 cm(-1) ) than deduced from recent experimental data. A further DIM-based correction is successfully tested for Ar-Cl(2) (the PES of which is shown in the picture) and predicts intervals D(0)(L)≈250±8 and D(0)(T)≈242±11 cm(-1) for Ar-I(2), which matches earlier experimental results.
ABSTRACT
A sub-monolayer of atomic sodium, Nan, was deposited on LiF(001) at 50 K and characterized by temperature-programmed desorption, X-ray photoelectron spectroscopy, and titration with HCl. The Nan was dosed with HCl to form (HCl)m..Nan/LiF(001), which was then irradiated by 640 nm laser-radiation to induce a charge-transfer (CT) reaction. Reaction-product atomic H(g) was observed leaving the surface, by two-color Rydberg-atom time-of-flight (TOF) spectroscopy. These H-atoms gave evidence of arising from the photoinduced harpooning reaction between the sodium clusters, Nan, on the substrate, and (HCl)m adsorbed on the Nan. The translational energy distribution, its vibrational structure, and the angular distribution of H(g) gave information regarding the harpooning event. Translationally and vibrationally excited HCl(g) was shown, by resonance-enhanced multiphoton ionization (REMPI), to be formed as an alternate product; by way of (HCl)m..Nan/LiF(001) + 602 nm-->(HCl)m - 1 Nan/LiF(001) + HCl(g)(v > or = 0).