Ionization and dissociation dynamics of vinyl bromide probed by femtosecond extreme ultraviolet transient absorption spectroscopy

Abstract

Strong-field induced ionization and dissociation dynamics of vinyl bromide, CH2=CHBr, are probed using femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy. Strong-field ionization is initiated with an intense femtosecond, near infrared (NIR, 775 nm) laser field. Femtosecond XUV pulses covering the photon energy range of 50-72 eV probe the subsequent dynamics by measuring the time-dependent spectroscopic features associated with transitions of the Br (3d) inner-shell electrons to vacancies in molecular and atomic valence orbitals. Spectral signatures are observed for the depletion of neutral C2H3Br, the formation of C2H3Br(+) ions in their ground (X̃) and first excited (Ã) states, the production of C2H3Br(++) ions, and the appearance of neutral Br ((2)P3/2) atoms by dissociative ionization. The formation of free Br ((2)P3/2) atoms occurs on a timescale of 330 ± 150 fs. The ionic à state exhibits a time-dependent XUV absorption energy shift of ∼0.4 eV within the time window of the atomic Br formation. The yield of Br atoms correlates with the yield of parent ions in the à state as a function of NIR peak intensity. The observations suggest that a fraction of vibrationally excited C2H3Br(+) (Ã) ions undergoes intramolecular vibrational energy redistribution followed by the C-Br bond dissociation. The C2H3Br(+) (X̃) products and the majority of the C2H3Br(++) ions are relatively stable due to a deeper potential well and a high dissociation barrier, respectively. The results offer powerful new insights about orbital-specific electronic processes in high field ionization, coupled vibrational relaxation and dissociation dynamics, and the correlation of valence hole-state location and dissociation in polyatomic molecules, all probed simultaneously by ultrafast table-top XUV spectroscopy.

Tracking dissociation dynamics of strong-field ionized 1,2-dibromoethane with femtosecond XUV transient absorption spectroscopy

“…[10][11][12] Simple haloalkanes have served as excellent benchmark systems for studying these interactions. [13][14][15][16][17][18][19] Understanding the effect of intense laser fields on molecules has important implications for several areas of fundamental chemistry such as coherent control of bond fission 20,21 and Coulomb explosion imaging. 22,23 In this work, femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy is used to explore the elimination dynamics of Br atoms and ions following strong field ionization (SFI) of 1,2-dibromoethane (DBE, C 2 H 4 Br 2 ).…”

Characterization of Photo-Induced Charge Transfer and Hot Carrier Relaxation Pathways in Spinel Cobalt Oxide (Co3O4)

“…(24)(25)(26) Taking cobalt oxide as an example, electronic structure changes occurring near cobalt atoms can be observed via the 58.9 eV cobalt M can be separated. Moreover, the development of the high harmonic generation (HHG) (27) technique enables conversion of widely available near-IR 800 nm pulses to XUV pulses with durations of femtoseconds (28)(29)(30) or even attoseconds. (31, 32) These short pulses can be utilized as an ideal tool for studying ultrafast photochemical processes in transition-metal-containing condensed-phase systems.…”

Coherent Electron Hole Dynamics Near a Conical Intersection

“…Therefore, the natural time scale for charge motion lies in the attosecond to femtosecond regime. Recent developments in attosecond, extreme ultraviolet (XUV) science provide new opportunities for the real-time investigation of electron dynamics in atomic [3][4][5][6] and molecular systems [7][8][9][10][11][12][13]. Specifically, by virtue of the high photon energy, ultrafast XUV pulses allow access to electron hole dynamics in photoionized molecules, an unexplored class of charge transfer phenomena [14][15][16].…”