Strong-Field Dissociative Double Ionization of Acetylene

Abstract

We investigate dissociative double ionization of acetylene, one of the smallest organic molecules yet with a rich electronic structure, in strong laser fields by measuring two fragment ions and two electrons in coincidence. The two-body fragmentation channels are dominated by the removal of electrons from the lower-lying molecular orbitals rather than from the highest occupied one. The electron localization-assisted enhanced ionization mechanism plays a central role for the strong-field deprotonation ionization of acetylene by releasing the second electron from the up-field potential well of the hydrogen site at the internuclear distance near twice the equilibrium value of the C-H bond.

Time-dependent density-functional study of the alignment-dependent ionization of acetylene and ethylene by strong laser pulses

“…The ionization of molecules with intense laser pulses is a complex process due to the interplay of the time-varying external potential introduced by the strong laser electric field and the Coulomb interaction between the electrons [1][2][3][4][5][6]. The final and seemingly close aim is not only understanding but also controlling the ionization dynamics to influence chemical reactions at the femtosecond time scale [7][8][9][10].…”

Channel-Resolved Above-Threshold Double Ionization of Acetylene

“…In particular, acetylene (C2H2) has attracted extensive interest as a prototype to study the isomerization process [22][23][24][25][26][27][28][29][30][31]. For acetylene-vinylidene isomerization, the proton can migrate from one carbon atom to the other on either the [22][23][24][25][26][27][28] or cation [29][30][31] states. Experimentally, the intermediate states for the proton migration are difficult to directly distinguish but are refered from the kinetic energy release (KER) of the ejected ionic fragments, as observed in previous experiments [22][23][24][25]29,31].…”

“…Among the mani fold photon-induced molecular dynamics, isomerization is one of the most fundamental and interesting processes [21]. In particular, acetylene (C2H2) has attracted extensive interest as a prototype to study the isomerization process [22][23][24][25][26][27][28][29][30][31]. For acetylene-vinylidene isomerization, the proton can migrate from one carbon atom to the other on either the [22][23][24][25][26][27][28] or cation [29][30][31] states.…”

Probing the role of excited states in ionization of acetylene

“…However, the cut-off energy for this inner plateau is lower than that predicted by the classical three-step model: we attribute this to suppression of ionization from the LUMO+1 due to transitions back to the HOMO-1 [66]. These transitions from the LUMO+1 to the HOMO-1 give rise to a window of enhanced harmonics (harmonics [11][12][13][14][15][16][17][18][19][20][21]. We can show that the inner plateau is due to the 3σ g → 3σ u transition rather than the 2σ u → 4σ g transition by calculating the contribution of each state to the harmonic response using Eq.…”

“…More recently, several studies have considered the response to strong fields. This has included single [16,17] and double [18,19] ionization, dissociative ionization of highly excited states [20], high harmonic generation [21][22][23][24] and more recently initiating isomerization of acetylene to vinylidene [25].…”