Imaging Charge Transfer in a Cation−π System: Velocity-Map Imaging of Ag⁺(benzene) Photodissociation

Abstract

Ag(+)(benzene) complexes are generated in the gas phase by laser vaporization and mass selected in a time-of-flight spectrometer. UV laser excitation at either 355 or 266 nm results in dissociative charge transfer (DCT), leading to neutral silver atom and benzene cation products. Kinetic energy release in translationally hot benzene cations is detected using a new instrument designed for photofragment imaging of mass-selected ions. Velocity-map imaging and slice imaging techniques are employed. In addition to the expected translational energy release, DCT of Ag(+)(benzene) produces a distribution of internally hot benzene cations. Compared with experiments at 355 nm, 266 nm excitation produces only slightly higher translational excitation and a much greater fraction of internally hot benzene ions. The maximum kinetic energy release in the photodissociation sets an upper limit on the Ag(+)(benzene) dissociation energy of 32.8 (+1.4/-1.5) kcal/mol.

Photofragmentation dynamics and dissociation energies of MoO and CrO

“…In most VMI photodissociation studies, the parent molecule is known due to the use of stable precursors 33 or (for charged species) massselectivity. 34,35 This is not the case here due to our use of laser ablation for producing a range of neutral Mo-containing species in the molecular beam. The identity of the co-fragment (and hence that of the signal carrier) can, however, be determined from the evolution of the VMI rings with excitation wavenumber.…”

Lanthanum-mediated dehydrogenation of 1- and 2-butynes: Spectroscopy and formation of La(C4H4) isomers

“…Spectroscopic characterization of metal-hydrocarbon radicals or ions formed in gas phase reactions has recently attracted considerable attention. Metal ion-hydrocarbon species are largely investigated by infrared or ultravioletvisible photodissociation or photoelectron spectroscopy, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] whereas metal atom-hydrocarbons are mainly studied by photoexcitation or photoionization techniques. [21][22][23][24][25][26][27][28][29][30][31][32] In principle, spectroscopic measurements could offer detailed information about metal-ligand bonding, molecular structures, and electronic states.…”

Velocity map ion imaging study of Ar2+ photodissociation

“…The SI-VMI instrument has been described previously [19]. It is based on our reflectron time-of-flight (RTOF) mass spectrometer that has been used for many years to study the photodissociation products and spectroscopy of mass-selected ions vertical polarization; Continuum SureLite SL-10), and reaccelerated using an assembly of electrostatic lenses configured for velocity map imaging [2].…”

“…Velocity and kinetic energy distributions may be used to study the partitioning of excess energy among the various internal degrees of freedom of the photofragments, and the nature of the electronic transition leading to photodissociation may be inferred from the angular distribution. While the field of photofragment imaging as applied to the photochemistry of neutral molecules has certainly come of age, very few ions have been studied in this way [12][13][14][15][16][17][18][19]. We have recently developed a new time-of-flight mass spectrometer for velocity-map imaging (VMI) [2] of the photofragments from mass-selected ions [19].…”

“…While the field of photofragment imaging as applied to the photochemistry of neutral molecules has certainly come of age, very few ions have been studied in this way [12][13][14][15][16][17][18][19]. We have recently developed a new time-of-flight mass spectrometer for velocity-map imaging (VMI) [2] of the photofragments from mass-selected ions [19]. We employ this new selected-ion VMI (SI-VMI) instrument here to study the photodissociation of the well-known argon dimer cation.…”