THEORY: Hemiquantal d ynamics w ith t he w hole DIM b asis (HWD)

1. Fragmentation Dynamics of Singly Ionized Homogeneous Rare Gas TrimersDaniel Hrivňák, Ivan Janeček and René KalusDepartment of Physics, University of Ostrava, Ostrava, Czech RepublicSupported by the Grant Agency of the Czech Republic (grant. no. 203/02/1204) DIM Method F. O. Ellison, J. Am. Chem. Soc. 85 (1963), 3540. P. J. Kuntz & J. Valldorf, Z. Phys. D (1987), 8, 195. SIMULATION II: Photodissociation of the vibrationally excited Rg3+ cluster Dissociation Photon absorption Heating hn The same configuration asprevious one. Cluster is excited to the higher electronic level. Vibrationally excited Rg3+ cluster on the basic electronic level. Stable configuration of the Rg3+ on the basic electronic level. Cluster is decayed to the single atoms. A general fragmentation pattern from experiment1, confirmed by our theoretical calculations at low temperatures: the middle atom obtains only a small velocity, two remaining outer atoms gain high velocities in opposite directions. The positive charge is usually localized on one of the fast outer atoms (the asymmetric fragmentation), but localization of the charge on the slow middle atom (the symmetric case) is observed too. An essential role in the theoretical and experimental results plays the spin-orbit splitting of the Rg+ ion to the two states 2P1/2 and 2P3/2 with some energetical gap. Xenon SO constant = 0.874 eV E(2P1/2) – E(2P3/2) = 1.311 eV D0(Xe3+) = 1.245 eV Argon SO constant = 0.117 eV E(2P1/2) – E(2P3/2) = 0.175 eV D0(Ar3+) = 1.592 eV 1Experiment: Haberland, Hofmann, and Issendorff, J. Chem. Phys. 103, 3450 (1995). PRAHA OSTRAVA THEORY:Hemiquantal dynamics with the whole DIM basis (HWD) M. Amarouche, F. X.Gadea, J. Durup, Chem. Phys. 130 (1989) 145-157 - multi-electronic-state molecular dynamics DIM extensions Diatomic inputs Neutral diatoms: empirical data Ar2 – R. A. Aziz, J. Chem. Phys. 99 (1993), 4518. Singly charged diatoms: computed ab initio by I. Paidarová and F. X. Gadéa (1996) The spin-orbit constant used is of empirical origin. DIM + SO [M. Amarouche et al., J. Chem. Phys. 88 (1988) 1010] The DIM model with inclusion of the spin-orbit coupling. [J. S. Cohen and B. Schneider, J. Chem. Phys. 64 (1974) 3230]. DIM + SO + ID-ID [M. Amarouche et al., J. Chem. Phys. 88 (1988) 1010]. Inclusion of the most important three-body forces corresponding to the interaction of two atomic dipoles induced by a positive charge localized on a third atom. SIMULATION I: Fragmentation of the Rg3+ cluster after sudden ionisation After dynamic equilibrisation the heated cluster has a random configuration different from initial one. A neutral trimer in static equilibrium configuration is vibrationally excited. Now, the trimer is suddenly ionised. (Red colour indicates positive charge localized on an atom in case diabatic Ionisation). The molecular dynamics continues up to 105 fs. In case of a cluster decay indication the dynamics is stopped. Table of average values Results 1: Role of spin-orbit coupling (SO), induced dipole - induced dipole interaction (ID-ID) and initial vibrational excitation (Ev) in Ar3+ decay Results 2: Comparison Ar3+, Kr3+ and Xe3+ decay. Initial heating of clusters to vibrational energy EV shortens time of decay, especially for disociation limit energy Edis, which is energy released in decay of neutral trimer on dimer and monomer. Energy E0 represent estimate of basic quantum vibration (“zero vibration”). For Ev=E0 none or sporadic fragmentations of Kr and Xe trimer ions are observed up to 105 fs. More frequent decaywas found forhigher initial vibrational excitation. Average values: <Q> - electric charge single Ar emitted, EKER – kinetic energy released, Evib, Erot, Etr – vibration, rotation and translation energy (REM – Ar2 remainder, EMIT –Ar emitted) The spin orbit coupling has major influence on decay. Time of decay is higher if SO is on. On the contrary a role of induced dipole – induced dipole interaction is not relevant. For Ev=Edis a fragmentation of population of the Ar3+ is very quick in comparisonwith Kr and Xe cases. * A. Bastida, N. Halberdstat, J.A. Beswick, F.X. Gadéa, U. Buck, R. Galonska, C. Lauenstein, Chem. Phys. Lett. 249 (1996)1-6