Gas-Phase Ion Dynamics and Chemistry

Abstract

While the physical chemistry of gas-phase ions has its roots in traditional mass spectrometry, the growth of the field during the past two decades can be attributed to the development and application of new experimental and theoretical techniques. Among these are guided ion beams for investigating ion−molecule reactions at very low translational energies, ion chromatography in which an ion’s electronic state or geometrical structure can be determined and selected, pulsed field ionization/zero kinetic energy photoelectron spectroscopy with ±0.1 meV resolution for determining ionization energies and ion vibrational frequencies, and multiphoton ionization and photoelectron−photoion coincidence methods for state selecting ions in uni- and bimolecular ionic reactions. The results from all of these studies have been greatly enhanced by concomitant advances in ab initio molecular orbital methods which provide heats of formation, structures, and vibrational frequencies of stable ion structures as well as transition states. This information is now widely used in interpreting collisional and unimolecular dissociation rates with the statistical theory, Rice−Ramsperger−Kassel−Marcus/quasiequilibrium theory. Near quantitative agreement between theory and experiment is now the norm. The confidence with which ion chemistry is now understood for small systems has permitted the application of these methods to molecular systems of interest in condensed phases and in organometallic and biological chemistry.

Gas-phase oon-molecule reactions of transition metal complexes: The effect of different coordination spheres on complex reactivity

“…Both synthetic products are confirmed by electrospraying the reaction mixture and observing the relevant (M ϩ H) ϩ peak (DIEN-(thioether) 2 , m/z 280; DIEN-(thio) 2 , m/z 296). In addition, 1 2 .…”

“…Both synthetic products are confirmed by electrospraying the reaction mixture and observing the relevant (M ϩ H) ϩ peak (DIEN-(thioether)(imi), m/z 272; DIEN-(thioether)(pyr), m/z 283). In addition, 1 The fifth group of ligands consists of DIEN-(THF) (pyr) and DIEN-(THF)(imi). These ligands are synthesized by first mixing 2-furaldehyde with DIEN in anhydrous methanol at a 1:1 ratio.…”

“…Because of this, ion molecule (I-M) experiments can be used to study the intrinsic properties of charged species and their chemical reactions [1][2][3][4]. Along with collision-induced dissociation (CID), I-M reactions can also be tools that provide structural information in a mass spectrometric experiment [5][6][7].…”

Mass resolved MPI spectra of methyl iodide in the 430–490 nm region

“…Resonance enhanced multiphoton ionization (REMPI) is a useful tool in the study of state specific reactions and in ion chemistry [1,2]. Methyl iodide, as the simplest molecule of alkyl iodides and a prototypical system for experimental investigation and theoretical model of photodissociation processes in polyatomic molecules [3,4], lots of multiphoton ionization and dissociation of the molecule have been studied [5][6][7][8][9][10][11][12][13][14][15][16][17].…”

Valence electronic structure and photofragmentation of 1,1,1,2-tetrafluoroethane (CF3-CH2F)

“…2 display vibrational structure indicating that the fragmentation subsequent to creation of these photoionized states occurs via predissociation [14,47], as these states are later seen to fragment. According to statistical unimolecular theories, the excess internal energy brought by photoionization is subsequently distributed between all degrees of freedom in the electronic ground state [48]. In the case of larger ionic molecules, this is typically achieved through rapid internal conversion to the electronic ground state [47].…”