Control of Electron Localization in Deuterium Molecular Ions using an Attosecond Pulse Train and a Many-Cycle Infrared Pulse

Abstract

We demonstrate an experimental control of electron localization in deuterium molecular ions created and dissociated by the combined action of an attosecond pulse train and a many-cycle infrared (IR) pulse. The attosecond pulse train is synthesized using both even and odd high order harmonics of the driving IR frequency so that it can strobe the IR field once per IR cycle. An asymmetric ejection of the deuterium ions oscillates with the full IR period when the APT-IR time-delay is scanned. The observed control is due to the creation of a coherent superposition of 1s sigma{g} and 2p sigma{u} states via interference between one-photon and two-photon dissociation channels.

Understanding the role of phase in chemical bond breaking with coincidence angular streaking

“…2a. It oscillates as a function of E k with a modulation contrast of B10%, about five times larger than reported in a recent pump-probe experiment 28 that employs an attosecond pulse train and a delayed infrared pulse. Figure 2c shows the dependence of b m on f el mol and E k .…”

“…A vibrational nuclear wavepacket on the 1ss g þ curve is created by the early part of the laser pulse at time t i . The wavepacket is coupled forth-and-back between the 2ps u þ and 1ss g þ states at later times (t c ) when the energy gap between the potential curves matches the photon energy (or three times the photon energy), with the molecular ion eventually dissociating into H þ þ H. Because of the coherent superposition of 1ss g þ and 2ps u þ contributions [20][21][22][23][24][25][26][27][28][29][30] , the electron probability density localizes asymmetrically at the nuclei. This electron localization dynamics is governed by the laser phase at the instant of field ionization (t i ) and by the coupling times t c,3o , t c,1o and t 0 c,1o , which depend on the chosen photon energy and on the shape of the potential energy curves involved.…”

“…The kinetic energy spectrum shifts when f el mol is changed by 180°. This is indicative of a kinetic-energy-dependent asymmetric dissociation or electron localization due to the interference between the 1o-and net-2o-dissociating wavepackets [20][21][22][23][24][25][26][27][28][29][30]32 .…”

“…The asymmetric fields drive and eventually localize the bound electron at one of the dissociating nuclei 25 . Alternatively, an attosecond pulse [26][27][28] is first used to launch a H 2 þ vibrational wavepacket by single-photon ionization of H 2 . Next, a phase-locked near-infrared laser pulse drives the remaining electron back and forth between the nuclei until it localizes at one of them, the choice of localization site being dependent upon the delay between the excitation and the driving pulses.…”

Intensity enhancement in the molecular ionization and dissociation dynamics in the presence of noise

“…In this area, many interesting phenomena have been revealed, including the bond softening and hardening [5,6], the electron localization in dissociation channels [7,8], the above threshold Coulomb explosion (CE) [9,10], the high-order harmonic generation (HHG) [11,12], the abovethreshold ionization (ATI) and dissociation (ATD) [13,14] etc. Usually, the ionization probabilities (IPs) and/or the dissociation probabilities (DPs) are critical to gain high signals or high yields for these photochemical and photophysical processes.…”