Breakdown Curves for Polyatomic Negative Ions

Abstract

Potential energy curves of ground and excited states of tetra halomethanes and the negative ionsNegative-ion breakdown curves were obtained at low (0-1 eV) energies for SFe and a number of fluorocarbons. The dissociation rate constants, as a function of internal energy of the parent negative ions, were computed for the processes observed and used to estimate kinetic shifts and thermochemical appearance potentials, at OaK, for the fragments. The results (e.g., metastable curve widths and temperature effects) were found to be in agreement with the quasiequilibrium theory (QET) of mass spectra. It is predicted that most of the parent negative ions studied (e.g., C7F 14 -from perfluoromethy1cyc1ohexane) would not fragment if formed by the capture of a thermal electron by the vibrationally cold molecule.

Metastable dissociative decay of fluorofullerene negative ions

“…The maxima of m* peaks arrange just between P − and D − peaks, which agrees with Ref. [21] (this observation is an analogy with the appearance energies of parent, metastable and daughter positive ions in conventional mass spectrometry [15]). …”

“…Undoubtedly, such distinguishing feature as long a of NI in the case of fullerene derivatives should be reflected on the character of their dissociative decay. Indeed, observed metastable (delayed in time) type of the NI fragmentation is another sure sign of relevance and applicability of the laws of statistical physics [15,21].…”

Atmospheric pressure anion mass spectrometry: electron affinities and activation energies of thermal electron attachment – perfluoromethylcyclohexane, C7F14

“…These data led to a lower limit of AE a (C 7 F 14 ) of 0.7 eV and apparent activation energy, E 1 (C 7 F 14 ), of 70 meV. In a 1984 dissertation, Shuie reported an AE a (C 7 F 14 ) of 1.4(2) eV from atmospheric pressure negative ion mass spectrometry (APINIMS) intensities of the c‐C 7 F 14 anion from 343K to 598K consistent with data from Lifshitz . Subsequently, Barrera used these data to report an AE a (C 7 F 14 ), 1.06(10) eV, listed in a 2004 compilation and constructed Herschbach Ionic Morse Person Electron Curves, HIMPEC, in the C 7 F 13 ‐F and C 6 F 11 ‐CF 3 dimensions .…”

Dissociation of Cyclobutane Molecule—Ions Formed in Charge Exchange Collisions

“…4 In the present study, we have utilized the QET to calculate the breakdown pattern for cyclobutane, employing the equations for the unimolecular reaction rate constant, k(E), given by Marcus,20,21 as previously described. 22 The details of the calculation procedure, parameters used, and assumptions made are described in the Appendix. Only primary dissociations of the cyclobutane ion were considered in these calculations.…”

“…The distribution was calculated in a manner previously described. 22 The vibrational frequencies of cyclobutane 30 and the parameters necessary for the calculation are known. 27a …”