Ionic dynamics underlying strong-field dissociative molecular ionization

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

doi:10.1103/physreva.96.023404

Cited by 4 publications

(5 citation statements)

References 33 publications

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“…We remark that nuclear dynamics was very recently confirmed to play a role in post-ionization excitation. 50,51 Future studies of the correlated photoelectron spectra as a function of intensity, pulse duration, and wavelength within a pump-probe scheme would be very helpful for developing a deeper understanding, in particular for photon energies above the gap energy. Finally, it would be interesting to explore how general our conclusions are by performing similar studies in other molecular systems.…”

Section: Discussionmentioning

confidence: 99%

Sequential and direct ionic excitation in the strong-field ionization of 1-butene molecules

Schell

Boguslavskiy

Schulz

et al. 2018

Phys. Chem. Chem. Phys.

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We study the Strong-Field Ionization (SFI) of the hydrocarbon 1-butene as a function of wavelength using photoion-photoelectron covariance and coincidence spectroscopy. We observe a striking transition in the fragment-associated photoelectron spectra: from a single Above Threshold Ionization (ATI) progression for photon energies less than the cation D0-D1 gap to two ATI progressions for a photon energy greater than this gap. For the first case, electronically excited cations are created by SFI populating the ground cationic state D0, followed by sequential post-ionization excitation. For the second case, direct sub-cycle SFI to the D1 excited cation state contributes significantly. Our experiments access ionization dynamics in a regime where strong-field and resonance-enhanced processes can interplay.

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Section: Discussionmentioning

confidence: 99%

Sequential and direct ionic excitation in the strong-field ionization of 1-butene molecules

Schell

Boguslavskiy

Schulz

et al. 2018

Phys. Chem. Chem. Phys.

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“…The collective observations in CPS(+) and CPS(−) suggest that, while the early portion of the pulse plays a role in the ultimate yield enhancement of Br + and I + involving intermediate neutral dynamics, the late portion of the pulse is responsible for the reduced yields in CH 2 Br + and CH 2 I + involving dynamics on the ionic surface. 42 Further examining the temporal structure of the full control pulses B and C shown in the background of Figure 5, it is evident that pulse B, which maximizes the objective ratio of Br + /CH 2 Br + , contains complex pulse structure over its entire temporal range; in contrast, pulse C, which produces a lower product ratio, is almost free of late-pulse features beyond ∼500 fs. Examination of these pulses further supports the CPS interpretation that, the late-pulse structure plays a central role in controlling the objective yield of Br + /CH 2 Br + .…”

Section: Experimental Cps Mechanism Analysismentioning

confidence: 99%

Section: Experimental Cps Mechanism Analysismentioning

confidence: 99%

Gaining Mechanistic Insight with Control Pulse Slicing: Application to the Dissociative Ionization of CH₂BrI

Rey-de-Castro

Rabitz

2017

J. Phys. Chem. A

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In quantum control experiments with shaped femtosecond laser pulses, adaptive feedback control is often used to identify pulse shapes that can optimally steer the quantum system toward the desired outcome. However, gaining mechanistic information can pose a challenge due to the varied structural features of the control pulses and/or the often complex nature of the associated simulations of the experiments. In this article, we introduce control pulse slicing (CPS) as an easy-to-implement experimental analysis tool that can be employed directly in the laboratory without the need for modeling, to gain mechanistic insights about control experiments, regardless of whether the pulse is optimal or chosen by other means. As an illustration, we apply CPS to dissociative ionization of CHBrI with mass spectral detection, where two pulses with similar intensities are investigated, with each capable of distinctively controlling the ratio of Br/CHBr. These two control pulses were, respectively, first identified with closed loop and open loop procedures, and then the multispecies experimental data was analyzed with CPS. By comparing the dynamical evolution of the observed multiple fragment ion yields upon slicing scans of the two distinct pulses, we were able to reveal insights about the control mechanism for manipulating the objective ratio. In addition, we also identified the relationship between the temporal structures of the control pulses and the associated key reaction pathways involved in ionic as well as neutral electronic states, in spite of the signals only directly being from the ionic species. The CPS technique is not limited to controlled fragmentation mass spectrometry, and it may be applied to gain mechanistic insights in any control experiment, reflected in the nature of the recorded signal.

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“…Experimental and theoretical works [22][23][24][25][26][27] on molecular fragmentation triggered by ionization suggest a positive answer to this question. Sudden ionization of a molecule creates a coherent superposition of electronic states, leading to ultrafast charge migration [28][29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

On the preservation of coherence in the electronic wavepacket of a neutral and rigid polyatomic molecule

Csehi

Badankó

Halász

et al. 2020

J. Phys. B: At. Mol. Opt. Phys.

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We present various types of reduced models including five vibrational modes and three electronic states for the pyrazine molecule in order to investigate the lifetime of electronic coherence in a rigid and neutral system. Using ultrafast optical pumping in the ground state (11Ag), we prepare a coherent superposition of two bright excited states, 11B2u and 11B1u, and reveal the effect of the nuclear motion on the preservation of the electronic coherence induced by the laser pulse. More specifically, two aspects are considered: the anharmonicity of the potential energy surfaces and the dependence of the transition dipole moments (TDMs) with respect to the nuclear coordinates. To this end, we define an ‘ideal model’ by making three approximations: (i) only the five totally symmetric modes move, (ii) which correspond to uncoupled harmonic oscillators, and (iii) the TDMs from the ground electronic state to the two bright states are constant (Franck–Condon approximation). We then lift the second and third approximations by considering, first, the effect of anharmonicity, second, the effect of coordinate-dependence of the TDMs (first-order Herzberg–Teller contribution), third, both. Our detailed numerical study with quantum dynamics is meant to be realistic for pyrazine over about 20 femtoseconds, and was further extended so as to probe the effect of such approximations on a model system. We show that long-term revivals of the electronic coherence persist up to the picosecond time range even for the most realistic model.

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Ionic dynamics underlying strong-field dissociative molecular ionization

Cited by 4 publications

References 33 publications

Sequential and direct ionic excitation in the strong-field ionization of 1-butene molecules

Sequential and direct ionic excitation in the strong-field ionization of 1-butene molecules

Gaining Mechanistic Insight with Control Pulse Slicing: Application to the Dissociative Ionization of CH₂BrI

On the preservation of coherence in the electronic wavepacket of a neutral and rigid polyatomic molecule

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Ionic dynamics underlying strong-field dissociative molecular ionization

Cited by 4 publications

References 33 publications

Sequential and direct ionic excitation in the strong-field ionization of 1-butene molecules

Sequential and direct ionic excitation in the strong-field ionization of 1-butene molecules

Gaining Mechanistic Insight with Control Pulse Slicing: Application to the Dissociative Ionization of CH2BrI

On the preservation of coherence in the electronic wavepacket of a neutral and rigid polyatomic molecule

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Gaining Mechanistic Insight with Control Pulse Slicing: Application to the Dissociative Ionization of CH₂BrI