Calculation of multiphoton ionization amplitudes and cross sections of few-electron atoms

Mihelič, A.; Horvat, Martin

doi:10.1103/physreva.103.043108

Cited by 3 publications

(1 citation statement)

References 39 publications

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“…Cross sections σ j connected to the dipole matrix elements for resonant excitation to the doubly excited state are calculated using the method of complex rotation [32], and cross sections for ionization of the doubly excited state are calculated using the methods from Refs. [59,60].…”

Section: Appendix B: Photoionization Cross Sectionsmentioning

confidence: 99%

XUV superfluorescence from helium gas in the paraxial three-dimensional approximation

et al. 2023

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We present the results of a theoretical study of XUV superfluorescence from doubly excited states of helium resonantly pumped by free-electron laser (FEL) pulses. Our model allows us to predict both the spectrum and angular distribution of emitted XUV radiation in a wide range of experimentally accessible parameters. This is achieved by going beyond two key deficiencies of most previous models: The one-dimensional treatment in space is upgraded to three dimensions with electromagnetic fields treated in the paraxial approximation and spontaneous emission is modeled by a recently developed approach that avoids the unrealistic delayed response but preserves the expected characteristics of the emitted field in the spontaneous emission limit. The case study of 3a 1 P o resonance in helium with 63.66 eV excitation energy is presented for realistic parameters of seeded light pulses from the FERMI FEL facility and a recently developed high-pressure gas cell. Results of numerical simulations show that both the spectral width and angular divergence of emitted radiation vary with gas pressure and pump pulse intensity in a complex way.

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Section: Appendix B: Photoionization Cross Sectionsmentioning

confidence: 99%

XUV superfluorescence from helium gas in the paraxial three-dimensional approximation

et al. 2023

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Single-photon and multi-photon Fano lines for helium and neon using tRecX-haCC

Chundayil,

Scrinzi,

Pramod Majety

2024

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

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Single-photon and multi-photon ionization of helium and neon atoms by ultrashort extreme ultraviolet radiation is studied. The wavelength of radiation is chosen to excite a set of doubly excited states. We analyse the lineshapes arising from the presence of doubly excited states and numerically demonstrate the sensitivity of the Fano $q$ parameter to the order of multi-photon process. The computations were performed using the {\tt tRecX-haCC} package developed by the authors. The {\tt tRecX-haCC} package solves the time-dependent Schr"odinger equation in the presence of a laser pulse and computes the photoelectron spectra including the narrow resonance peaks using the tSurff and iSurf techniques.

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Interference of two-photon transitions induced by XUV light

Žitnik

Mihelič

Bučar

et al. 2022

Optica

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The relative phase of first ( ω 1 ) and third harmonics ( ω 3 ) extreme ultraviolet light pulses was varied to control the population of the 2 s 2 state in helium through the interference of ω 1 + ω 1 and ω 3 − ω 1 two-photon excitation paths. The population was monitored by observing the total electron yield due to the 2 s 2 autoionization decay. Maximum yield occurs when the relative phase of the two harmonics matches the phase difference of complex atomic amplitudes governing the two excitation paths. The calculated trend of atomic phase differences agrees well with the measured data in the spectral region of the resonance, provided that time-reversed − ω 1 + ω 3 path is also taken into account. These results open the way to accessing phase differences of two-photon ionization paths involving energetically distant intermediate states and to perform interferometry in the extreme ultraviolet range by monitoring final state populations.

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Calculation of multiphoton ionization amplitudes and cross sections of few-electron atoms

Cited by 3 publications

References 39 publications

XUV superfluorescence from helium gas in the paraxial three-dimensional approximation

XUV superfluorescence from helium gas in the paraxial three-dimensional approximation

Single-photon and multi-photon Fano lines for helium and neon using tRecX-haCC

Interference of two-photon transitions induced by XUV light

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