Imaging of the umbrella motion and tunneling in ammonia molecules by strong-field ionization

Förster, Johann; Plésiat, Étienne; Magana, Alvaro; Sáenz, Alejandro

doi:10.1103/physreva.94.043405

Cited by 11 publications

(10 citation statements)

References 37 publications

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“…These spectroscopy methods provide a powerful approach to characterizing vibrational eigenfrequencies for harmonic modes, but do not directly access bond lengths and angles. Similar limitations apply to the so-called Lochfrass or 'R-dependent ionization' spectroscopies, where the ground state is selectively depleted as a function of some key structural parameter [9][10][11][12].…”

mentioning

confidence: 99%

Ultrafast X-Ray Scattering Measurements of Coherent Structural Dynamics on the Ground-State Potential Energy Surface of a Diplatinum Molecule

et al. 2019

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mentioning

confidence: 99%

Ultrafast X-Ray Scattering Measurements of Coherent Structural Dynamics on the Ground-State Potential Energy Surface of a Diplatinum Molecule

et al. 2019

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“…In the present work, we demonstrate LIED's capability to image the motion of hydrogen atoms on the few-fs timescale by studying the umbrella (inversion) motion of the ammonia molecule (NH3) following its strong-field ionization. Photoelectron spectra and photoionization-induced dynamics of individual ammonia molecules and clusters have been a topic of interest in the past decades, both experimentally [31][32][33][34][35] and theoretically [34][35][36][37][38][39][40] . Neutral ammonia at its equilibrium configuration has a pyramidal shape, described by the 𝐶 #$ symmetry point group, with an equilibrium H-N-H bond angle 41 , F !"!…”

Section: Introductionmentioning

confidence: 99%

Laser-induced electron diffraction of the ultrafast umbrella motion in ammonia

Belsa

Amini

Liu

et al. 2021

Structural Dynamics

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Visualizing molecular transformations in real-time requires a structural retrieval method with Ångström spatial and femtosecond temporal atomic resolution. Imaging of hydrogen-containing molecules additionally requires an imaging method sensitive to the atomic positions of hydrogen nuclei, with most methods possessing relatively low sensitivity to hydrogen scattering. Laser-induced electron diffraction (LIED) is a table-top technique that can image ultrafast structural changes of gas-phase polyatomic molecules with sub-Ångström and femtosecond spatiotemporal resolution together with relatively high sensitivity to hydrogen scattering. Here, we image the umbrella motion of an isolated ammonia molecule (NH 3 ) following its strong-field ionization. Upon ionization of a neutral ammonia molecule, the ammonia cation (NH 3 + ) undergoes an ultrafast geometrical transformation from a pyramidal ( 107 ) to planar ( 120 ) structure in approximately 8 femtoseconds. Using LIED, we retrieve a near-planar ( 117 5 ) field-dressed NH 3 + molecular structure 7.8 9.8 femtoseconds after ionization. Our measured field-dressed NH 3 + structure is in excellent agreement with our calculated equilibrium field-dressed structure using quantum chemical ab initio calculations.

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“…Finally, we show results for NH 3 in the pyramidal and planar geometries. These latter results form benchmark data for tunneling ionization with which other results in the literature [48] can be compared. Since in high-harmonic spectroscopy applications of the WFAT the phase of the structure factor is important [22][23][24], we emphasize that we show the structure factor and not its norm squared as in previous publications [26,30,39,49].…”

Section: Resultsmentioning

confidence: 83%

“…In an oscillating field, the direction of the field alternates, equivalent to β = 0 and 180 deg, and the average value of the ratio of the rates is ∼6.9, which can be compared with the ratio of ∼5-8 (at 1 × 10 13 -6 × 10 13 W/cm 2 ) obtained from the frozen nuclei TDSE calculations reported in Ref. [48].…”

Section: B Moleculesmentioning

confidence: 78%

“…As a final example of the usefulness of the present IR approach, we consider the example of NH 3 , which has not been considered before with the WFAT. Recently, there was some interest in imaging the umbrella motion in NH 3 by strong-field ionization [48]. In that work, ionization yields were obtained by frozen nuclei time-dependent Schrödinger equation (TDSE) model calculations as a function of the inversion coordinate.…”

Section: B Moleculesmentioning

confidence: 99%

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Structure factors for tunneling ionization rates of molecules: General Hartree-Fock-based integral representation

et al. 2017

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In the leading-order approximation of the weak-field asymptotic theory (WFAT), the dependence of the tunneling ionization rate of a molecule in an electric field on its orientation with respect to the field is determined by the structure factor of the ionizing molecular orbital. The WFAT yields an expression for the structure factor in terms of a local property of the orbital in the asymptotic region. However, in general quantum chemistry approaches molecular orbitals are expanded in a Gaussian basis which does not reproduce their asymptotic behavior correctly. This hinders the application of the WFAT to polyatomic molecules, which are attracting increasing interest in strong-field physics. Recently, an integral-equation approach to the WFAT for tunneling ionization of one electron from an arbitrary potential has been developed. The structure factor is expressed in an integral form as a matrix element involving the ionizing orbital. The integral is not sensitive to the asymptotic behavior of the orbital, which resolves the difficulty mentioned above. Here, we extend the integral representation for the structure factor to many-electron systems treated within the Hartree-Fock method and show how it can be implemented on the basis of standard quantum chemistry software packages. We validate the methodology by considering noble-gas atoms and the CO molecule, for which accurate structure factors exist in the literature. We also present benchmark results for CO 2 and for NH 3 in the pyramidal and planar geometries.

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Imaging of the umbrella motion and tunneling in ammonia molecules by strong-field ionization

Cited by 11 publications

References 37 publications

Ultrafast X-Ray Scattering Measurements of Coherent Structural Dynamics on the Ground-State Potential Energy Surface of a Diplatinum Molecule

Ultrafast X-Ray Scattering Measurements of Coherent Structural Dynamics on the Ground-State Potential Energy Surface of a Diplatinum Molecule

Laser-induced electron diffraction of the ultrafast umbrella motion in ammonia

Structure factors for tunneling ionization rates of molecules: General Hartree-Fock-based integral representation

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