Dependence on the Initial Configuration of Strong Field-Driven Isomerization of C₂H₂ Cations and Anions

Abstract

We have investigated the femtosecond laser-induced fragmentation of C2H2 q ion beam targets in various initial configurations, including acetylene (linear HCCH), vinylidene (H2CC), and cis/trans. The initial configuration is shown to have a tremendous impact on the branching ratio of acetylene-like (CH q 1 + CH q 2 ) and vinylidene-like (C q 1′ + CH2 q 2′) dissociation of a specific C2H2 q molecular ion. In particular, whereas C2H2 + generated from C2H2, a linear HCCH target, exhibits comparable levels of acetylene-like and vinylidene-like fragmentation, vinylidene or cis/trans configuration ion beams preferably undergo vinylidene-like fragmentation, with an acetylene branching ratio ranging from 13.9% to zero.

Spectroscopy of Radicals, Clusters, and Transition States Using Slow Electron Velocity-Map Imaging of Cryogenically Cooled Anions

“…As shown schematically in Figure a, it lies 1.925 eV above acetylene and can isomerize to HCCH over a small (0.13 eV) barrier. − The isomerization reaction is the simplest 1,2-hydrogen shift and is thus a benchmark chemical reaction . This consideration has motivated many experimental ,− and theoretical − studies of how the vibrational energy levels of H 2 CC and HCCH are coupled to one another. One approach to this problem has been to map out the excited vibrational energy levels of HCCH that lie above the H 2 CC minimum and search for perturbations with H 2 CC levels. ,, A more direct approach, developed by Lineberger, makes use of the fact that H 2 CC – is the stable anionic form of H 2 CC and that photodetachment of this species directly accesses the neutral H 2 CC well, corresponding to the X̃ 1 A 1 state of vinylidene.…”

Controlling H3+ Formation From Ethane Using Shaped Ultrafast Laser Pulses

“…The intramolecular migration of hydrogen continues to be an active area of investigation in ultrafast science [1][2][3][4][5][6][7][8][9][10][11] with implications for topics ranging from combustion [12] to peptide dissociation [13] and characterizing conformational differences in molecules [14,15]. In some cases the migration of hydrogen leads to the formation of new molecular ions, such as H + 3 [5,[16][17][18][19][20][21], by processes such as H 2 roaming or double hydrogen migration [18,19,22,23].…”

Importance of one- and two-photon transitions in the strong-field dissociation of NO2+

“…+ is [60]. Other examples include cis-trans acetylene [61] and vinylidene molecules [62][63][64][65], which may be produced as metastable ion beams.…”