Threshold Collision-Induced Dissociations for the Determination of Accurate Gas-Phase Binding Energies and Reaction Barriers

Leucine enkephalin—A mass spectrometry standard

“…Ionization energies are relatively easily determined with conventional EI studies; accuracy can be increased with special instrumentation and/or photoionization (Armentrout & Baer, 1996;Ervin, 2001;Armentrout, 2003;Bodi et al, 2009). Determination of appearance energy (the minimum energy required to observe a fragmentation product) is also feasible.…”

“…The breakdown curve is shown to much higher collision energies than the SY curve, because the spectra change even after all molecular ions have decomposed; mainly due to consecutive reactions. Analogous breakdown curves can be derived as a function of the center-of-mass collision energy (useful in fundamental studies, especially under single-collision conditions (Armentrout, 2003), excitation amplitude (used in ion traps) or also as a function of mean internal energy. Breakdown curves as a function of mean internal energy would be most desirable, but are rarely available experimentally.…”

Cluster reactivity experiments: Employing mass spectrometry to investigate the molecular level details of catalytic oxidation reactions

“…A variety of cluster formation methods, primarily including laser vaporization (LaVa) (10)(11)(12), pulsed-arc discharge (PACIS) (13)(14)(15), electrospray ionization (ESI) (16), gas aggregation (17)(18), and inert gas sputtering (CORDIS) (18) have enabled the creation of both positively and negatively charged as well as neutral gas-phase clusters across a large size range and with diverse elemental composition. The thermodynamic properties of clusters, including bond-dissociation energies (19)(20)(21), endothermic-reaction barriers (22), heat capacities (23), and the enthalpy, entropy, and free-energy changes associated with clustering reactions (24,25), including those composed of hydrogen-bonded and van der Waals systems, have been widely studied, employing both GIB-MS and flow-tube experiments. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR) (26) along with other linear ion trapping techniques (27) have been used to investigate the time-dependent kinetics of cluster molecule reactions, providing insight into reaction mechanisms, activation energies, and reaction intermediates.…”

Classical trajectories and RRKM modeling of collisional excitation and dissociation of benzylammonium and tert-butyl benzylammonium ions in a quadrupole-hexapole-quadrupole tandem mass spectrometer

“…It is interesting to note that both energy distributions have markedly nonthermal character, i.e., they cannot be approximated with a Boltzmann distribution without neglecting their distinctive shapes. Also, for illustrative purposes, Figure 4S in the Supporting Information compares this distribution with the functional form of the internal energy distribution used by Armentrout and coworkers (e.g., refs [11,20,[43][44][45][46]). …”

“…An informative review of studies directed at determining energy distributions resulting from collisional ion activation is given in [18]. In a series of studies, Armentrout and coworkers investigated collision-induced dissociation of small polyatomic ions under the conditions of low pressures, where most ions experience only single collisions with the inert collider gas (e.g., references [11,20,43,44]. These authors concentrated on determination of reaction threshold energies, and performed RRKM modeling of the experimental data using a functional form of the internal energy distribution derived from a theoretical analysis of an empirical model of the collisional energy dependences of the effective reaction cross sections [45,46].…”