Crossed Beam Photodissociation Imaging of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>HeH</mml:mi><mml:mo>+</mml:mo></mml:msup></mml:math>with Vacuum Ultraviolet Free-Electron Laser Pulses

Pedersen, H. B.; Altevogt, S.; Jordon-Thaden, Brandon; Heber, O.; Rappaport, M.; Schwalm, D.; Ullrich, J.; Zajfman, D.; Treusch, R.; Guerassimova, N.; Martins, M.; Hoeft, J.; Wellhöfer, M.; Wolf, A.

doi:10.1103/physrevlett.98.223202

Cited by 54 publications

(72 citation statements)

References 30 publications

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“…In addition to extremely accurate knowledge of the spectroscopic properties of the hydrohelium cation, the various mechanisms leading to its formation or decay must be investigated to obtain a correct estimation of the population of the levels. In this context, the first experimental data for the photodissociation cross section in the far UV have been obtained recently using the free electron laser FLASH at Hambourg (Pedersen et al 2007), showing important disagreement with the previous theoretical works and motivating new calculations (Sodoga et al 2009, Dumitriu andSaenz 2009).…”

Section: Introductionmentioning

confidence: 94%

Ab initiocalculation of the 66 low-lying electronic states of HeH⁺: adiabatic and diabatic representations

Loreau¹,

Liévin²,

Palmeri³

et al. 2010

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

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Using the quantum chemistry package MOLPRO and an adapted basis set, we have calculated the adiabatic potential energy curves of the first 20 1 + , 19 3 + , 12 1 , 9 3 , 4 1 and 2 3 electronic states of the HeH + molecular ion in CASSCF and CI approaches. The results are compared with previous works. The radial and rotational non-adiabatic coupling matrix elements as well as the dipole moments are also calculated. The asymptotic behaviour of the potential energy curves and of the various couplings between the states is also studied. Using the radial couplings, the diabatic representation is defined and we present an example of our diabatization procedure on the 1 + states.

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Section: Introductionmentioning

confidence: 94%

Ab initiocalculation of the 66 low-lying electronic states of HeH⁺: adiabatic and diabatic representations

Loreau¹,

Liévin²,

Palmeri³

et al. 2010

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

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“…The experimental scheme developed for exploring X-ray fragmentation of molecular ions at FLASH with the TIFF ion facility ("Trapped Ion Fragmentation at FLASH") [27,28] is shown in Figure 1. The FEL beam, approximately half-way between a focusing mirror and the platform foreseen for experiments with the focused beam, is crossed by an ion beam of ∼2-8 keV kinetic energy, fast enough to let photofragments travel on in a forward cone around the ion beam direction.…”

Section: Apparatusmentioning

confidence: 99%

“…The FLASH measurements have triggered two theoretical studies [38,39] which confirm the excited Π potential curves of HeH + as the dominant states for [27]. Only the distant detector D2 was used at 0.987-m distance from the beam crossing point, deflecting any charged fragments before D2.…”

mentioning

confidence: 99%

“…The first HeH + photodissociation measurements with TIFF [27] were performed in 2006 at 38.7 eV photon energy, slightly below the onset of photoionization, with typical pulse energies of 10 µJ and ∼25 HeH + ions in the crossing region during a FEL pulse. Within the limited photon beam time available, fragmentation momenta of atomic He fragments could be measured for ∼700 signal events, deriving distributions of the kinetic energy release and of the fragmentation angle in the center-of-mass (c.m.)…”

mentioning

confidence: 99%

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Soft-x-ray fragmentation studies of molecular ions

Wolf¹,

Pedersen²,

Lammich³

et al. 2010

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

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Abstract. Imaging of photofragments from molecular ions after irradiation by soft X-ray photons has been realized at the ion beam infrastructure TIFF set up at the FLASH facility. Photodissociation of the two-electron system HeH + at 38.7 eV revealed the electronic excitations and the charge-state ratios for the products of this process, reflecting the non-adiabatic dissociation dynamics through multiple avoided crossings among the HeH + Rydberg potential curves. Dissociative ionization of the protonated water molecules H 3 O + and H 5 O + 2 at 90 eV revealed the main fragmentation pathways after the production of valence vacancies in these ionic species, which include a strong three-body channnel with a neutral fragment (OH + H + + H + ) in H 3 O + photolysis and a significant two-body fragmentation channel (photolysis. The measurements yield absolute cross sections and fragment angular distributions. Increased precision and sensitivity of the technique was realized in recent developments, creating a tool for exploring X-ray excited molecular states under highly controlled target conditions challenging detailed theoretical understanding.

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“…Intense XUV pulses were, e.g., applied on rare gases to study sequential versus non-sequential multiple ionization [24,25], and creation of charge states up to 21 in Xe was observed [21]. For molecules, experiments on HeH + [26] and N 2 [27] provided benchmark data for theory. The high-frequency regime is defined in this work as the regime where one-photon ionization is allowed.…”

mentioning

confidence: 99%

Characterization of Molecular Breakup by Very Intense Femtosecond XUV Laser Pulses

Yue

Madsen

2015

Phys. Rev. Lett.

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We study the breakup of H + 2 exposed to super-intense, femtosecond laser pulses with frequencies greater than that corresponding to the ionization potential. By solving the time-dependent Schrödinger equation in an extensive field parameter range, it is revealed that highly nonresonant dissociation channels can dominate over ionization. By considering field-dressed Born-Oppenheimer potential energy curves in the reference frame following a free electron in the field, we propose a simple physical model that characterizes this dissociation mechanism. The model is used to predict control of vibrational excitation, magnitude of the dissociation yields, and nuclear kinetic energy release spectra. Finally, the joint energy spectrum for the ionization process illustrates the energy sharing between the electron and the nuclei and the correlation between ionization and dissociation processes. [8,9], and rescattering induced dissociation [10]. All these processes were discovered in the low-frequency regime where absorption of several photons is needed to reach a breakup channel. Depending on the laser parameters, either dissociation or ionization dominates [11][12][13].With advancements in light-source technology, extreme-ultraviolet (XUV) laser pulses of femto-and subfemtosecond duration are now produced from highorder harmonic [14][15][16][17] or free-electron lasers [18,19]. New focusing techniques [20][21][22] led to XUV femtosecond (fs) pulses with peak intensities I ≥ 4 × 10 17 W/cm 2 [23]. Intense XUV pulses were, e.g., applied on rare gases to study sequential versus non-sequential multiple ionization [24,25], and creation of charge states up to 21 in Xe was observed [21]. For molecules, experiments on HeH + [26] and N 2 [27] provided benchmark data for theory. The high-frequency regime is defined in this work as the regime where one-photon ionization is allowed. Since the photon resonance is much closer to the threshold for ionization than for dissociation, ionization is at first glance expected to dominate.Here we characterize some hitherto unobserved molecular breakup phenomena in the regime of super-intense, high-frequency, fs pulses, supplementing the phenomena known from the low-frequency regime, and adding insight to the general field of strong laser-matter interaction. The characteristics we find include (a) even with full inclusion of nuclear dynamics, stabilization against ionization occurs, i.e., the ionization yield does not necessarily increase with intensity [28,29]; (b) a mechanism by which dissociation, in contrast to the expectation from energy considerations, completely dominates over ionization; (c) control over the vibrational distribution, dissociation yield, and nuclear kinetic energy release (NKER) spectra by the parameters of the laser pulse; (d) insight into the energy sharing between electronic and nuclear degrees of freedom, as displayed by the joint energy spectrum (JES).We consider H + 2 , a molecule that was used to discover many low-frequency processes that were later observed in m...

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Crossed Beam Photodissociation Imaging ofHeH+with Vacuum Ultraviolet Free-Electron Laser Pulses

Cited by 54 publications

References 30 publications

Ab initiocalculation of the 66 low-lying electronic states of HeH⁺: adiabatic and diabatic representations

Ab initiocalculation of the 66 low-lying electronic states of HeH⁺: adiabatic and diabatic representations

Soft-x-ray fragmentation studies of molecular ions

Characterization of Molecular Breakup by Very Intense Femtosecond XUV Laser Pulses

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Crossed Beam Photodissociation Imaging ofHeH+with Vacuum Ultraviolet Free-Electron Laser Pulses

Cited by 54 publications

References 30 publications

Ab initiocalculation of the 66 low-lying electronic states of HeH+: adiabatic and diabatic representations

Ab initiocalculation of the 66 low-lying electronic states of HeH+: adiabatic and diabatic representations

Soft-x-ray fragmentation studies of molecular ions

Characterization of Molecular Breakup by Very Intense Femtosecond XUV Laser Pulses

Contact Info

Product

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Ab initiocalculation of the 66 low-lying electronic states of HeH⁺: adiabatic and diabatic representations

Ab initiocalculation of the 66 low-lying electronic states of HeH⁺: adiabatic and diabatic representations