Journal of Chemical Physics, Vol.117, No.9, 4299-4305, 2002
Charge transfer reactions between chiral Rydberg atoms and chiral molecules
Charge exchange reactions between a thermal beam of laser excited chiral Rydberg atoms of rubidium and nozzle jet expanded (resolved) chiral enantiomers of a series of carbonyl, cyanide, and halide containing molecules are studied. Chiral Rydberg atoms (oriented atoms with selected M-J) are produced using two-photon excitation of high nd D-2(5/2) Rydberg states of a beam of rubidium atoms using right- and left-circularly polarized light. Chiral anions of (S)-2-methylbutanenitrile, (R)-3-methylcyclopentanone, and (R)-3-methylcyclohexanone are produced in a narrow range of specific values of n(*) (effective principal quantum number) characteristic of dipole bound negative ions. These data are used to obtain electron affinities of 12.6, 3.3, and 4.2 meV, respectively. The electron affinities derived for (R)-3-methylcyclopentanone and (R)-3-methylcyclohexanone are confirmed from measurements of their electric field detachment thresholds. (R)-3-methylcyclohexanone also shows a second bound dipole anion state with an electron affinity of 8.8 meV. The two separate dipole bound anions are attributed to two different conformers (equatorial and axial -CH3) of 3-methylcyclohexanone present in the nozzle jet expansion. Rydberg reactions with partially resolved [enantiomeric excess (ee)similar to30%] (R)-2-iodooctane undergo dissociative electron attachment to produce the I- ion. Similarly, Rydberg reactions with partially resolved (eesimilar to54%) (R)-bromochlorofluoromethane undergo dissociative electron attachment to produce both Br- and Cl-ions. No differences (at the level of >5%) are observed in the charge transfer rate for the reaction of opposite enantiomers of the Rydberg atom with resolved enantiomers for all of the chiral molecules studied.