Ion-molecule reactions of excitedand ground-state Fe+ with NO are reported. The charge-exchange and clustering ion-molecule reactions of Fe+ with Fe(CO)5 are used to study the reaction dynamics of metastable versus ground electronic state Fe+ ions. The ground-state 6D(4s'3d6) Fe+ ions are unreactive with NO. Conversely, the metastable electronic states react with NO to form charge-transfer product ions (NO+) and radiative association adduct ions [Fe+(NO)] and by the collisional relaxation process. The collisional relaxation process gives rise to the groundstate 6D(4s'3d6) and excited-state 6S(4s1 23d5) Fe+ ions. The 6S(4s23d5) Fe+ ion is unreactive with NO and constitutes approximately 6% of the Fe+ ion population. Molecular orbital concepts are used to explain the lack of reactivity for the 6S(4s23d5) Fe+ ions and also the collisional relaxation process by the high-lying 4s'3d6 states to form the 6S(4s23d5) Fe+ ions.

respective polynuclear aromatic hydrocarbon counterparts. This phenomenon remains to be further investigated. Finally, the sensitive nature of chiral recognition by CDx's may be used to provide further insight into the binding or interaction of third components in CDx/heterocyclic systems. Warner, I. M. J. Phys. Chem. 1991, 95, 4897. Phys. Chem. 1990, 94, 5020. 1981. (1) Schuette, J. M.; Ndou, T. T.; Mufioz de la Pefia, A.; Greene, K. L.; (2) Bergmark, W. R.; Davis, A.; York, C.; Macintosh, A.; Jones, G. 11. J. (3) Lin, S.-F. Ph.D. Dissertation, University of Wisconsin in Madison, (4) Matsui, Y.; Mochida, K. Bull. Chem. SOC. Jpn. 1979, 52, 2808. (5) Szejtli, J. Cyclodextrins and Their Inclusion Complexes; Akademiai (6) Schuette, J. M.; Ndou, T. T.; Warner, I. M. J. Am. Chem. SOC., in (7) Mufioz de la Pefia, A.; Ndou, T. T.; Zung, J. B.; Greene, K. L.; Live, (8) Zung, J. B.; Ndou, T. T.; Mufioz de la Pefia, A.; Warner, I. M. J. Phys. (9) Ishizuka, Y.; Nagawa, Y.; Nakanishi, H.; Akira, K. J. Inclusion (10) Kobayashi, N.; Opallo, M. J. Chem. SOC. Commun. 1990, 477. (11) Ata, M.; Kubozono, Y.; Suzuki, Y.; Aoyagi, M.; Gondo, Y. Bull. Kiado: Budapest, 1982. press. D. H.; Warner, I. M. J . Am. Chem. SOC. 1991, 113, 1572. Chem. 1991, 95, 6701.Charge-exchange ion-molecule reactions of Fe' with Fe(C0)5 formed by 20-70-eV electron impact of Fe(C0)5 are reported. The charge-exchange reaction chemistry data indicate that electronic states with energies up to about 4.0 eV are produced and that 40% of the excited-state ions are in the first excited state 4F(3d7) and the remaining 60% are in the 4D(4s13d6) to *G(4s'3d6) or higher energy states. Of the Fe+ produced by 50-70-eV ionizing energy 65% are formed as excited states and about 35% as ground state 6D(4s'3d6). The results from charge-exchange ion-molecule reactions are compared to the excited states determined by other methods.

The overall rate constants for collisional relaxation of metastable excited states of Fe(+) by He, Ar, Kr, H2, (2)H2, CO, N2, NO, CH4, and CH3OH have been studied by using charge-exchange ion-molecule reaction chemistry. The rate constants vary according to the nature of the quenching reagent as well as the energy level and electron configuration of the Fe(+) ions. In general, NO, CH4, and CH3OH are the most efficient quenching reagents with rate constants that approach the Langevin collision rate, whereas the reaction rates for the rare gas atoms are slow and vary depending upon the specific electron configuration of the Fe(+) ion. The mechanism of collisional relaxation is discussed with emphasis on a curve-crossing. mechanism for the rare gas atoms. An electron-transfer mechanism is described for the relaxation of high lying (Fe(+))*.

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