Time-resolved nuclear dynamics in bound and dissociating acetylene

Abstract

We have investigated nuclear dynamics in bound and dissociating acetylene molecular ions in a time-resolved reaction microscopy experiment with a pair of few-cycle pulses. Vibrating bound acetylene cations or dissociating dications are produced by the first pulse. The second pulse probes the nuclear dynamics by ionization to higher charge states and Coulomb explosion of the molecule. For the bound cations, we observed vibrations in acetylene (HCCH) and its isomer vinylidene (CCHH) along the CC-bond with a periodicity of around 26 fs. For dissociating dication molecules, a clear indication of enhanced ionization is found to occur along the CH- and CC-bonds after 10 fs to 40 fs. The time-dependent ionization processes are simulated using semi-classical on-the-fly dynamics revealing the underling mechanisms.

Coincident angle-resolved state-selective photoelectron spectroscopy of acetylene molecules: a candidate system for time-resolved dynamics

“…Among important aspects of the physics of systems beyond the Born-Oppenheimer approximation 4 , decoupling nuclear and electronic dynamics, the role of conical intersections 5 , shape resonances 6 , and fast rearrangements within molecules [7][8][9] are of particular interest. Proton migration ensuing in the rearrangement of photoexcited molecular systems has a prominent place not only owing to the intriguing The acetylene-vinylidene system has long served as the benchmark for investigations of isomerization especially on ultrafast timescales 7,14,15 as well as in static spectroscopy and theoretical investigations [16][17][18][19] . Both the photoexcitation of outer-valence electrons 7 in the extreme-ultraviolet as well as core-shell electrons in the hard-xray regimes can effect isomerization 8 .…”

Ultrafast Laser-Induced Isomerization Dynamics in Acetonitrile

“…Coulomb explosion imaging (CEI) is a unique method to investigate molecular dynamics, where the system is multiply ionized, and upon Coulomb explosion, the kinetic energy of the constituent ionic fragments are directly measured . Due to its applicability to a large variety of molecular systems, CEI is widely used, especially when combined with other techniques such as pump–probe , or coincidence spectroscopy, and has recently been applied to directly visualize conical intersections and probe molecular dissociation dynamics . A more in-depth discussion of our specific experimental setup is given in the Methods section.…”

Ultrafast nuclear dynamics of the acetylene cation C2H2+ and its impact on the infrared probe pulse induced C–H bond breaking efficiency

“…[12][13][14][15][16][17][18][19][20] In a recent study, the nuclear dynamics following strong-field ionization of the acetylene molecule was investigated using the Coulomb explosion technique. 18 The elaborated experimental setup and advanced calculations allowed the extraction of information about bond length oscillations on the ground state of the acetylene cation initiated by the excitation process and to connect them with the observed fragment yields. In the present work, the ultrafast molecular dynamics in acetylene following photoexcitation to an excited state is studied with few-femtosecond resolution in a pump-probe experiment using an attosecond XUV pump and a few-cycle IR probe pulse.…”

“…It is known that the variations of the yields of different fragmentation channels with pump-probe delay reflect the fast nuclear motion occurring on the few-tens-of-femtosecond timescale. [3][4][5]18,19,21 This letter focuses on the nuclear motion after ionization leading to the modulation of the C 2 H + fragment yield probed by IR irradiation. Using electronic structure computations and dynamical simulations, we were able to identify the different reaction pathways leading to C-H dissociation and assess the impact of nuclear rearrangements on the different IR-induced mechanisms leading to either an enhancement or a quenching of the C 2 H + fragment yield.…”