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Ursrey, D.; Anis, Fatima; Esry, B. D.

doi:10.1103/physreva.85.023429

Cited by 21 publications

(21 citation statements)

References 35 publications

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“…The methods used for the solution will be outlined here, but are described in more detail in our previous work [44,48]. The electric field is treated classically, and the length gauge is used within the dipole approximation.…”

Section: A Born-oppenheimer Representation For the Time-dependent Scmentioning

confidence: 99%

“…In this paper, we will take advantage of the generality of the photon-phase representation to extend our under-standing of coherent control to a new system: HeH + , the simplest heteronuclear molecule with an electronic asymmetry in the standard Born-Oppenheimer approximation. We have previously shown [44] that exposing HeH + to long-wavelength pulses (longer than roughly λ = 2000 nm) produces dissociation probabilities that are large enough to realistically measure provided the intensity approaches I = 10 14 W/cm 2 . These relatively large dissociation probabilities, coupled with the fact that HeH + ion beams have been shown to be viable experimental targets [45][46][47], make both experimental and theoretical studies on CEP control of HeH + dissociation reasonable.…”

Section: Introductionmentioning

confidence: 99%

“…These relatively large dissociation probabilities, coupled with the fact that HeH + ion beams have been shown to be viable experimental targets [45][46][47], make both experimental and theoretical studies on CEP control of HeH + dissociation reasonable. Moreover, HeH + is a particularly interesting molecule to study because its dissociation is dominated by permanent dipole effects in this regime [44]. This property makes HeH + different from the vast majority of molecules studied in intense laser fields, which are dominated by electronic transitions.…”

Section: Introductionmentioning

confidence: 99%

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Using the carrier-envelope phase to control strong-field dissociation of HeH+ at midinfrared wavelengths

Ursrey

Esry

2017

Phys. Rev. A

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We study the response of HeH + to an intense, few-cycle laser pulse. Specifically, we present the carrier-envelope phase dependence of the kinetic energy release spectrum, the spatial asymmetry, and the total dissociation probability in two-cycle pulses with an intensity of 10 14 W/cm 2 and wavelengths of 3200 nm and 4000 nm. Strong spatial asymmetries are found in spite of the fact that the electron always becomes localized as He+H + , demonstrating that control of such asymmetries can be obtained via control of the nuclear degrees of freedom-as opposed to its usual interpretation as control over the electronic degrees of freedom. We explain these CEP effects in terms of our photon-phase representation.

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Section: A Born-oppenheimer Representation For the Time-dependent Scmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Using the carrier-envelope phase to control strong-field dissociation of HeH+ at midinfrared wavelengths

Ursrey

Esry

2017

Phys. Rev. A

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“…The large permanent dipole moment allows direct transfer of population from lower to higher vibrational states, which results in stretching of the molecule on the femtosecond timescale [13]. Electronic excitation, on the other hand, is negligible [20] due to the large energy difference between the electronic ground state X 1 Σ + and the first excited state A 1 Σ + , see Fig. 1.…”

mentioning

confidence: 99%

Heteronuclear Limit of Strong-Field Ionization: Fragmentation of HeH+ by Intense Ultrashort Laser Pulses

et al. 2018

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The laser-induced fragmentation dynamics of this most fundamental polar molecule HeH^{+} are measured using an ion beam of helium hydride and an isotopologue at various wavelengths and intensities. In contrast to the prevailing interpretation of strong-field fragmentation, in which stretching of the molecule results primarily from laser-induced electronic excitation, experiment and theory for nonionizing dissociation, single ionization, and double ionization both show that the direct vibrational excitation plays the decisive role here. We are able to reconstruct fragmentation pathways and determine the times at which each ionization step occurs as well as the bond length evolution before the electron removal. The dynamics of this extremely asymmetric molecule contrast the well-known symmetric systems leading to a more general picture of strong-field molecular dynamics and facilitating interpolation to systems between the two extreme cases.

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“…This is based on the intuition that the field-free rotational timescale of picoseconds is much greater than the vibrational timescale of fs and thus rotational motion can be safely neglected.However, as several works employing semiclassical methods [7,18,19] have shown, rotational dynamics are crucial for the understanding of the angular distribution of the final ion fragments. Even at lower intensities where ionization is negligible and pure dissociation is the dominating fragmentation process, it was shown that molecular rotations play a role [20][21][22][23][24] for pulses as short as ∼ 5 fs.For our studies, we choose to focus on the simplest stable polar molecule, HeH + , sketched in Fig. 1(d).…”

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confidence: 99%

Strong-field polarizability-enhanced dissociative ionization

et al. 2018

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We investigate dissociative single and double ionization of HeH + induced by intense femtosecond laser pulses. By employing a semi-classical model with nuclear trajectories moving on field-dressed surfaces and ionization events treated as stochastical jumps, we identify a strong-field mechanism wherein the molecules dynamically align along the laser polarization axis and stretch towards a critical internuclear distance before getting dissociative ionized. As the tunnel-ionization rate is greater for larger internuclear distance and for aligned samples, ionization is enhanced. The strong dynamical rotation is traced back to a maximum in the parallel component of the internucleardistance-dependent polarizability tensor. Qualitative agreement with our experimental observations is found. Finally the criteria for observing the isotope effect for the ion angular distribution is discussed.PACS numbers: 33.80. Wz, 33.80.Eh, 42.50.Hz The ionization and dissociation of small molecules in intense laser fields is of fundamental interest and has captured the attention of physicists for many years [1][2][3]. When the ratio of the laser frequency to the peak electric field is sufficiently small, the ionization process can be considered as an electron tunneling through the instantaneous barrier formed by the field and the Coulomb potential of the system [4]. In molecules, such tunnelionization rates depend on the spatial separation between the nuclei [5-9], as well as the molecular orientation with respect to the laser polarization axis, where the ionization rate follows the shape of the highest-occupied molecular orbital [10][11][12]. In addition to these fixed-nuclei properties, the molecules will dynamically rotate and stretch in the field, potentially leading to fragmentation [8]. Here, we theoretically identify a new fragmentation pathway that involves the combination of the aforementioned strong-field dynamics. Namely, due to the force resulting from the internuclear-distance-dependent polarizability tensor, the molecule is simultaneously aligned and stretched towards a specific internuclear distance in the field-dressed ground state before being ionized. We denote it as polarizability-enhanced dissociative ionization (PEDI) and support our findings with experimental data.Polarizability effects have been explored extensively in strong-field physics, e.g. it has regularly appeared in the interpretation of strong-field ionization experiments [13,14], and the anisotropic polarizability is often exploited in molecular alignment experiments [15][16][17]. In dissociative ionization studies involving short laser pulses (tens of femtoseconds (fs) duration), often only the vibrational degrees of freedom are considered, while the rotational dynamics are disregarded. This is based on the intuition that the field-free rotational timescale of picoseconds is much greater than the vibrational timescale of fs and thus rotational motion can be safely neglected.However, as several works employing semiclassical methods [7,18,19] have show...

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Multiphoton dissociation of HeH+below the He+(1s)+H(1s

Cited by 21 publications

References 35 publications

Using the carrier-envelope phase to control strong-field dissociation of HeH+ at midinfrared wavelengths

Using the carrier-envelope phase to control strong-field dissociation of HeH+ at midinfrared wavelengths

Heteronuclear Limit of Strong-Field Ionization: Fragmentation of HeH+ by Intense Ultrashort Laser Pulses

Strong-field polarizability-enhanced dissociative ionization

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