Nonadiabatic dynamics and multiphoton resonances in strong-field molecular ionization with few-cycle laser pulses

Tagliamonti, Vincent; Sándor, Péter; Zhao, Arthur; Rozgonyi, Tamás; Marquetand, Philipp; Weinacht, Thomas

doi:10.1103/physreva.93.051401

Cited by 25 publications

(27 citation statements)

References 44 publications

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“…"# ratio is again near unity. However, at intermediate UP, where non-adiabatic ionization strongly contributes to the ionization yield [64][65][66][67][68] all three gases exhibit an enhancement in ionization for counter-rotating laser fields. Note that the low UP behavior in argon differs from helium and krypton.…”

Section: Iiia Experimental Resultsmentioning

confidence: 99%

Observation of ionization enhancement in two-color circularly polarized laser fields

et al. 2017

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When atoms are irradiated by two-color circularly polarized laser fields the resulting strong field processes are dramatically different than when the same atoms are irradiated by a single-color ultrafast laser. For example, electrons can be driven in complex 2D trajectories before rescattering or circularly polarized high harmonics can be generated, which was once thought impossible. Here, we show that two-color circularly polarized lasers also enable control over the ionization process itself and make a surprising finding: the ionization rate can be enhanced by up to 700% simply by switching the relative helicity of the two-color circularly polarized laser field. This enhancement is experimentally observed in helium, argon and krypton over a wide range of intensity ratios of the twocolor field. We use a combination of advanced quantum and fully classical calculations to explain this ionization enhancement as resulting in part due to the increased density of excited states available for resonance-enhanced ionization in counter-rotating fields compared with co-rotating fields. In the future, this effect could be used to probe the excited state manifold of complex molecules.

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Section: Iiia Experimental Resultsmentioning

confidence: 99%

Observation of ionization enhancement in two-color circularly polarized laser fields

et al. 2017

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“…For example, optical spectroscopies, such as transient absorption [24][25][26][27][28], can provide high time resolution with a compact apparatus but require detailed knowledge of the potential energy surfaces (electronic energies as a function of nuclear coordinates) and transition dipole moments along the reaction coordinate in order to be interpreted. Time-resolved ionization spectroscopies [23,[29][30][31][32][33][34][35][36] offer the advantage over optical spectroscopies that it is always possible to ionize, regardless of the character of the excited-state, and if one measures the energy of the photoelectrons as a function of pump-probe delay, then one can extract information about the distribution of energy within the molecule as a function of time. UED [37][38][39][40][41][42][43] holds the promise of providing direct structural information as a function of time, but it suffers from orientational averaging over the sample, repulsion between the electrons in a short pulse, and the group velocity mismatch between electrons and light.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic and Structural Probing of Excited-State Molecular Dynamics with Time-Resolved Photoelectron Spectroscopy and Ultrafast Electron Diffraction

et al. 2020

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Pump-probe measurements aim to capture the motion of electrons and nuclei on their natural timescales (femtoseconds to attoseconds) as chemical and physical transformations take place, effectively making "molecular movies" with short light pulses. However, the quantum dynamics of interest are filtered by the coordinate-dependent matrix elements of the chosen experimental observable. Thus, it is only through a combination of experimental measurements and theoretical calculations that one can gain insight into the internal dynamics. Here, we report on a combination of structural (relativistic ultrafast electron diffraction, or UED) and spectroscopic (time-resolved photoelectron spectroscopy, or TRPES) measurements to follow the coupled electronic and nuclear dynamics involved in the internal conversion and photodissociation of the polyatomic molecule, diiodomethane (CH 2 I 2). While UED directly probes the 3D nuclear dynamics, TRPES only serves as an indirect probe of nuclear dynamics via Franck-Condon factors, but it is sensitive to electronic energies and configurations, via Koopmans' correlations and photoelectron angular distributions. These two measurements are interpreted with trajectory surface hopping calculations, which are capable of simulating the observables for both measurements from the same dynamics calculations. The measurements highlight the nonlocal dynamics captured by different groups of trajectories in the calculations. For the first time, both UED and TRPES are combined with theory capable of calculating the observables in both cases, yielding a direct view of the structural and nonadiabatic dynamics involved.

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“…The ponderomotive potential is estimated to be approximately 0.5-0.7 eV based on previous work [24,29]. …”

Section: Resultsmentioning

confidence: 99%

“…Pulses with octave-spanning bandwidth (400-900 nm at the tails) are produced through supercontinuum generation in argon gas [29,36]. To compress the pulses and produce durations of less than 10 fs, we use an AOMbased pulse shaper in a 4f geometry [34,37] and perform a multiphoton intrapulse interference phase scan (MIIPS) to retrieve the optical phase [38][39][40][41][42].…”

Section: Experimental Apparatusmentioning

confidence: 99%

“…1. This picture is based on our earlier calculations and measurements [24,29], which indicate that an excited neutral (Rydberg) state (R 1 ), correlated with the first excited state of the cation (D 1 ), comes into resonance during the laser pulse. The reaction coordinate in this picture is the CH 2 wagging mode, which was found to be the only one for which there was significant displacement of excited state minima at the Franck-Condon (FC) point, and crossing between states facilitating nonadiabatic transitions.…”

Section: Introductionmentioning

confidence: 99%

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Time-resolved measurement of internal conversion dynamics in strong-field molecular ionization

et al. 2017

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We time-resolve coupled electronic and nuclear dynamics during strong-field molecular ionization by measuring the momentum-resolved photoelectron yield as a function of pump-probe delay for a pair of strong-field laser pulses. The sub-10 fs pulses are generated using a specially designed ultrafast optical pulse shaper and the electrons are measured using velocity map imaging. Our measurements, in conjunction with calculations that solve the time-dependent Schrödinger equation, allow us to time-resolve resonance enhanced strong-field ionization and break it down into three basic steps: (1) Stark shifted resonant excitation of a high-lying neutral state of the molecule, (2) nonadiabatic dynamics (internal conversion) in which multiple electronic states are coupled, and (3) coupling to the continuum (ionization).

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Nonadiabatic dynamics and multiphoton resonances in strong-field molecular ionization with few-cycle laser pulses

Cited by 25 publications

References 44 publications

Observation of ionization enhancement in two-color circularly polarized laser fields

Observation of ionization enhancement in two-color circularly polarized laser fields

Spectroscopic and Structural Probing of Excited-State Molecular Dynamics with Time-Resolved Photoelectron Spectroscopy and Ultrafast Electron Diffraction

Time-resolved measurement of internal conversion dynamics in strong-field molecular ionization

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