The Jahn-Teller effect in the 3pe' Rydberg state of H3: review of experimental and ab initio determinations.

The dissociative recombination (DR) of H(3)(+) ions with electrons, producing neutral atomic and molecular fragments, is driven primarily by the vibronic Jahn-Teller (JT) interaction between the electronic components of the pe' e(-)-H(3)(+) collision (Rydberg) channel. The JT parameters characterizing this interaction are therefore of great interest as they are required for the theoretical predictions of the DR cross section. In this contribution, we review various determinations of these quantities that have been made previously, based both on spectroscopic studies of 3pe' Rydberg-excited H(3) states, and on the analysis of the corresponding ab initio H(3) Rydberg potential surfaces near the conical intersection (D(3h) symmetry) for n=3-5. The highly correlated theoretical 3pe' potential surfaces of Mistrík et al. are used for a new determination of both the linear and quadratic JT terms.

On the (Emultiply sign in circlee)-Jahn-Teller conical intersections in the 3p(E') and 3d(E") Rydberg electronic states of triatomic hydrogen.

The static and dynamic aspects of the Jahn-Teller (JT) interactions in the 3p(E') and 3d(E") Rydberg electronic states of H3 are analyzed theoretically. The static aspects are discussed based on recent ab initio quantum chemistry results, and the dynamic aspects are examined in terms of the vibronic spectra and nonradiative decay behavior of these states. The adiabatic potential-energy surfaces of these degenerate electronic states are derived from extensive ab initio calculations. The calculated adiabatic potential-energy surfaces are diabatized following our earlier study on this system in its 2p(E') ground electronic state. The nuclear dynamics on the resulting conically intersecting manifold of electronic states is studied by a time-dependent wave-packet approach. Calculations are performed both for the uncoupled and coupled state situations in order to understand the importance of nonadiabatic interactions due to the JT conical intersections in these excited Rydberg electronic states.

Collision photography: polarization imaging of atom-molecule collisions.

We report differential scattering experiments on the laser excitation of Na + M collision pairs with M = N(2), CO, C(2)H(2), and CO(2). The collision event is probed by the laser polarization revealing geometric and electronic properties of the collision pair. The experimental data are compared to the results of a Monte Carlo trajectory simulation using ab initio quantum chemical data.

Nonadiabatic coupling and vector correlation in dissociation of triatomic hydrogen.

We determine experimentally the vector correlation among the three neutral ground state hydrogen atoms which appear in dissociation of neutral H3* molecules. The sum of the kinetic energies of the three H-atoms is fixed by selecting the energy of the H3* molecule by laser excitation in the range between 0.85 and 3.60 eV. The highly structured maps of correlation in the motion of the three atoms provide a direct view of the internal molecular couplings which initiate dissociation. We discuss this feature in a model calculation and in terms of a new quantum chemical calculations of the potential energy surfaces of H3*.

Activation of pig liver esterase in organic media with organic polymers: application to the enantioselective acylation of racemic functionalized secondary alcohols.

Pig liver esterase (PLE) shows practically no activity in acylation of alcohols with vinylic esters in organic solvents. However, addition of methoxypoly(ethylene glycol) (MPEG), bovine serum albumin (BSA), TentaGelAmino resin (TGA), or aminomethyl polystyrene (AMPS) confers activity to PLE in acylation of alcohols with vinyl propionate in organic solvents of low water content. Polymer-activated PLE showed high enantioselectivities (E > 100) in the acylation of racemic 1-alkoxy-, 1-ethylsulfanyl-, and 1-fluoro-3-aryl-2-propanols as well as racemic 1-phenoxy-2-propanol and racemic 1-methoxy-2-phenoxy-2-propanol. The synthetic utility of polymer-activated PLE has been demonstrated by the gram-scale resolution of 1-methoxy-3-phenyl-2-propanol, 1-ethylsulfanyl-3-phenyl-2-propanol, 1-methoxy-3-p-methoxyphenyl-2-propanol, 1-fluoro-3-phenyl-2-propanol, and 1-methoxy-3-phenoxy-2-propanol. In PLE-catalyzed acylation of alcohols with vinyl propionate, acetaldehyde and propionic acids, both being detrimental to the enzyme, are formed as byproducts. In addition, the water content of the system, which is critical for the activity of pig liver esterase, is lowered because of a competing enzymatic hydrolysis of the acyl donor. The polymers TGA, BSA, and AMPS not only scavenge the aldehyde and the acid through imine formation and neutralization, respectively, but replenish at least in part also the water consumed in the competing hydrolysis of the acyl donor. A recovery of PLE together with the polymer was achieved without major loss of activity through their immobilization on a water-saturated polyaramide membrane, which occurs spontaneously in organic solvents.