aneous rupture of both bonds. The action spectrum consists of two broad peaks between the atomic transition of Mg+(3 2P←3 2S). Ab initio calculations show a minimum-energy structure, in which Mg+ attaches to the O atom and one of the three F atoms of 2,2,2-trifluoroethanol, forming a five-membered ring. The calculated absorption spectrum corresponding to the minimum-energy structure agrees nicely with the experimental action spectrum. The branching fractions of the photoproducts are approximately constant in a given spectral range, but they change significantly across the spectral ranges. The constant branching fractions point to the ground state reactions following traversals from the initially accessed excited states through conical intersections. On the other hand, the observation of the electronic state-specific branching fractions is explained by the orbital alignments of the excited electron, which is dictated by the five-membered ring structure of the complex.

Acetonitrile-solvated Mg+ complexes Mg+(NCCH3)n were produced in a pick-up source. The Mg+(NCCH3)n clusters were subjected to photodissociation in a time-of-flight reflectron mass spectrometer. Except for a minor reactive product Mg1-NC at short wavelengths, only nonreactive (or evaporation) fragments were observed from photodissociation of Mg1 (NCCH3) n (n=1-4). Action spectra of Mg+(NCCH3)n (n=1-4) were recorded in the spectral region of 230-560nm, which provide insight into the structure and photodissociation dynamics of the complexes. For all the complexes we studied, the ligands are believed to be in the first solvation shell. Both the evaporation and reaction processes occur on the ground state surfaces of the complexes. By using the DFT/B3LYP and CIS methods, the most stable ground-state structures and the excitation spectra for Mg+(NCCH3) 1-3 were obtained. The ab initio predictions appear to be consistent with the experimental results.

The hydride abstraction reaction in the Mg+-NH2CH3 complex has been investigated by using the DFT and MP2 methods. Two local minima and two transition states have been found along the reaction pathway. Accompanied with IRC calculations, the reaction is revealed to be a three-step process, i. e., a hydrogen-migration process followed by a charge-transfer process and a nonreactive-dissociation process. On the basis of single-point calculations using CCSD (T) in conjunction with 6-311++G (d, pd) basis set with the geometries optimized at B3LYP/6-311++G** with zero point energy (ZPE) corrections, the reaction energies for all the steps are predicted.

The resonance-enhanced multip hoton ionization (REMPI) spect rum of 2-but anone in 467～488nm was obt ained using multiphoton ionization-time-of-flight mass spect rometric technique and dye laser. By analyzing the spectrum, we have ascert ained that thest rongest peak in the REMPI spectrum, 62305cm-1, could be at tributed to one component of the 3d Rydberg transition, the peaks in 63291～63898cm-1 are mixed Rydberg-valence vibronic transitions, and 63291cm-1 is the 0-0 transition of the state.

We present the photodissociation spectroscopy of the complexes of Mg+ with di- and tri-ethylamine in the spectral range of 230-440nm. Mass spectrometry of the two parent complexes exhibits the persistent product Mg+ from nonreactive quenching throughout the whole wavelength range. As for the reactive channels, C3H7-elimination products are dominant when the complexes are excited to 3Px,y. Furthermore, photoexcitation of Mg+-NH(C2H5)2 to 3Px,y yields a minor MgH-elimination fragment. On the other hand, photodissociation of Mg+-N(C2H5)3 produces charge-transfer fragments N+(C2H5)3 and (C2H5)2N+CH2. The action spectra of the two complexes consist of two pronounced peaks on the red and blue side of the Mg+ 3 2P←3 2S atomic transition. The calculated absorption spectra of the two complexes using the optimized structures of their ground states agree nicely with the observed action spectra. Photofragment branching fractions of the products are shown to be nearly independent of the photon energy for the 3Px,y excitation, indicating the importance of exit channel effects. A photoreaction mechanism is proposed for C3H7-elimination, which entails Mg1 insertion into one C-N bond, followed by a nonadiabatic transition to the ground-state surface through a conical intersection. However, for the MgH-elimination channel in the photodissociation of Mg+NH(C2H5)2, Mg+ rather inserts into the a-C-H bond. Finally, photoexcitation of Mg+-N(C2H5)3 leads to a prominent charge-transfer product [N+(C2H5)3]*, which dissociates further to (C2H5)2N+CH2 by a loss of CH3.