arXiv:1401.5503

Two-color pump-probe dynamics of transitions between doubly excited states of Helium

Spyros I. Themelis

Published Jan 21, 2014• 0 citations

Abstract

We discuss the dynamics of the two-photon resonant ionization of helium involving two autoionizing states in the presence of two-color laser fields. The first source is tuned around the transition from the ground state to the 2s2p 1Po autoionizing state, and the second couples the state 2s2p 1Po to the 2p2 1S autoionizing state. The laser coupling between the doubly excited states is shown to lead to modifications of the Beutler-Fano profile and the appearance of an Autler-Townes doublet. This double resonance effect between autoionizing states can be observed at moderate laser intensities easily attainable by currently operated sources.

DOI: 10.48550/arxiv.1401.5503

Related papers

Ionization dynamics in double resonance involving autoionizing states in helium: the effect of pulse shapes

Spyros I. Themelis, P. Lambropoulos, M. Meyer

Journal of Physics B Atomic Molecular and Optical PhysicsOct 27, 200440 citations

Laser-assisted-autoionization dynamics of helium resonances with single attosecond pulses

Wei-Chun Chu, Song-Feng Zhao, C. D. Lin

arXiv:1205.4775Physical Review ASep 29, 201140 citations

Doubly-Excited Helium Strongly Driven with Short and Long Wavelength Pulses

Alexander Magunia

Jan 1, 20180 citations

Attosecond Transient Absorption Spectroscopy of doubly-excited states in helium

Luca Argenti, Christian Ott, Thomas Pfeifer +1 more

arXiv:1211.2566Nov 12, 20122 citations

Coupling of autoionizing states by a chirped laser pulse

M. Žitnik, A. Mihelič, K. Bučar +11 more

Synopsis We have observed the autoionization of the laser-coupled 2s2p 1 Po and 2p 2 1 Se resonances in helium. The ions were collected while varying the frequency and delay of the extreme-ultraviolet (EUV) excitation pulse with respect to the linearly chirped visible (VIS) laser pulse. From the measured frequency-delay map the Autler-Townes splitting, the EUV-VIS cross-correlation and the linear chirp parameter were extracted.

Journal of Physics Conference SeriesJan 1, 20200 citations

Theoretical study of double-resonance processes in the helium continuum

Alessandro Lami, N. K. Rahman, Pietro Spizzo

Physical Review ASep 1, 19897 citations

arXiv:1401.5503

Two-color pump-probe dynamics of transitions between doubly excited states of Helium

Spyros I. Themelis

Published Jan 21, 2014• 0 citations

arXiv HTML PDF

Abstract

DOI: 10.48550/arxiv.1401.5503

Related papers

Ionization dynamics in double resonance involving autoionizing states in helium: the effect of pulse shapes

Spyros I. Themelis, P. Lambropoulos, M. Meyer

We discuss the dynamics of doubly resonant ionization in helium involving the strong coupling of two doubly excited autoionizing resonances, under the influence of XUV radiation of short duration (DESY FEL) and a synchronized optical laser. We explore the possibility of using the photoelectron spectra to extract information about the pulse shape of the FEL. We present in addition new calculations of the expected AC Stark splitting due to the strong coupling of the two resonances and show that, within the range of intensities and pulse durations expected in the experiments, additional structure, beyond the usual doublet, is to be expected.We discuss the dynamics of doubly resonant ionization in helium involving the strong coupling of two doubly excited autoionizing resonances, under the influence of XUV radiation of short duration (DESY FEL) and a synchronized optical laser. We explore the possibility of using the photoelectron spectra to extract information about the pulse shape of the FEL. We present in addition new calculations of the expected AC Stark splitting due to the strong coupling of the two resonances and show that, within the range of intensities and pulse durations expected in the experiments, additional structure, beyond the usual doublet, is to be expected.

Journal of Physics B Atomic Molecular and Optical PhysicsOct 27, 200440 citations

Laser-assisted-autoionization dynamics of helium resonances with single attosecond pulses

Wei-Chun Chu, Song-Feng Zhao, C. D. Lin

The strong coupling between two autoionizing states in helium is studied theoretically with the pump-probe scheme. An isolated 100-as XUV pulse is used to excite helium near the $2s2p{(}^{1}\phantom{\rule{0.16em}{0ex}}P)$ resonance state in the presence of an intense infrared (IR) laser. The laser field introduces strong coupling between $2s2p{(}^{1}\phantom{\rule{0.16em}{0ex}}P)$ and $2{p}^{2}{(}^{1}\phantom{\rule{0.16em}{0ex}}S)$ states. The IR also can ionize helium from both autoionizing states. By changing the time delay between the XUV and the IR pulses, we investigated the photoelectron spectra near the two resonances. The results are used to explain the recent experiment by Gilbertson et al. [Phys. Rev. Lett. 105, 263003 (2010)]. Using the same isolated attosecond pulse and a 540-nm laser, we also investigate the strong coupling between $2s2p{(}^{1}\phantom{\rule{0.16em}{0ex}}P)$ and $2{s}^{2}{(}^{1}\phantom{\rule{0.16em}{0ex}}S)$ by examining how the photoelectron spectra are modified versus the time delay and the possibility of observing Autler-Townes doublet in such experiments.The strong coupling between two autoionizing states in helium is studied theoretically with the pump-probe scheme. An isolated 100-as XUV pulse is used to excite helium near the $2s2p{(}^{1}\phantom{\rule{0.16em}{0ex}}P)$ resonance state in the presence of an intense infrared (IR) laser. The laser field introduces strong coupling between $2s2p{(}^{1}\phantom{\rule{0.16em}{0ex}}P)$ and $2{p}^{2}{(}^{1}\phantom{\rule{0.16em}{0ex}}S)$ states. The IR also can ionize helium from both autoionizing states. By changing the time delay between the XUV and the IR pulses, we investigated the photoelectron spectra near the two resonances. The results are used to explain the recent experiment by Gilbertson et al. [Phys. Rev. Lett. 105, 263003 (2010)]. Using the same isolated attosecond pulse and a 540-nm laser, we also investigate the strong coupling between $2s2p{(}^{1}\phantom{\rule{0.16em}{0ex}}P)$ and $2{s}^{2}{(}^{1}\phantom{\rule{0.16em}{0ex}}S)$ by examining how the photoelectron spectra are modified versus the time delay and the possibility of observing Autler-Townes doublet in such experiments.

arXiv:1205.4775Physical Review ASep 29, 201140 citations

Doubly-Excited Helium Strongly Driven with Short and Long Wavelength Pulses

Alexander Magunia

Within this work, electron dynamics of autoionizing, doubly excited states in helium are investigated. Therefore, strong field couplings of these states are studied in two spectral regimes: in the infrared and in the extreme ultraviolet. A laser system capable of tuning its output-pulses' central wavelength within the infrared spectral regime is installed and characterized by a FROG setup. Furthermore, high harmonics of these output pulses are generated and discussed. First intensity dependent and time resolved experiments in helium with this laser system are presented and supported by numerical calculations. The transition from an unperturbed light induced state, which is generated from the 2p4p state, to a resonant Autler-Townes splitting of the sp2;3+ state is observed. Furthermore, strong field couplings between the ground and a doubly-excited state are studied in the extreme ultraviolet only regime. With the help of simulations Rabi-like couplings and Stark shifts for ultrashort pulses leading to a manipulated absorption line shape are investigated. The same study is carried out for autoionizing states. This theory part is used to explain experimentally measured line-shape changes of the 2s2p resonance in helium interacting with FEL pulses.Within this work, electron dynamics of autoionizing, doubly excited states in helium are investigated. Therefore, strong field couplings of these states are studied in two spectral regimes: in the infrared and in the extreme ultraviolet. A laser system capable of tuning its output-pulses' central wavelength within the infrared spectral regime is installed and characterized by a FROG setup. Furthermore, high harmonics of these output pulses are generated and discussed. First intensity dependent and time resolved experiments in helium with this laser system are presented and supported by numerical calculations. The transition from an unperturbed light induced state, which is generated from the 2p4p state, to a resonant Autler-Townes splitting of the sp2;3+ state is observed. Furthermore, strong field couplings between the ground and a doubly-excited state are studied in the extreme ultraviolet only regime. With the help of simulations Rabi-like couplings and Stark shifts for ultrashort pulses leading to a manipulated absorption line shape are investigated. The same study is carried out for autoionizing states. This theory part is used to explain experimentally measured line-shape changes of the 2s2p resonance in helium interacting with FEL pulses.

Jan 1, 20180 citations

Attosecond Transient Absorption Spectroscopy of doubly-excited states in helium

Luca Argenti, Christian Ott, Thomas Pfeifer +1 more

Strong-field manipulation of autoionizing states is a crucial aspect of electronic quantum control. Recent measurements of the attosecond transient absorption spectrum of helium dressed by a few-cycle visible pulse [Ott et al., arXiv:1205.0519[physics.atom-ph] ] provide evidence of novel ultrafast resonant phenomena, namely, two-photon Rabi oscillations between doubly-excited states and the inversion of Fano profiles. Here we present the results of accurate \emph{ab-initio} calculations that agree with these observations and in addition predict that (i) inversion of Fano profiles is actually periodic in the coupling laser intensity and (ii) the supposedly dark $2p^2$ { $^1$ S} state also appears in the spectrum. Closer inspection of the experimental data confirms the latter prediction.Strong-field manipulation of autoionizing states is a crucial aspect of electronic quantum control. Recent measurements of the attosecond transient absorption spectrum of helium dressed by a few-cycle visible pulse [Ott et al., arXiv:1205.0519[physics.atom-ph] ] provide evidence of novel ultrafast resonant phenomena, namely, two-photon Rabi oscillations between doubly-excited states and the inversion of Fano profiles. Here we present the results of accurate \emph{ab-initio} calculations that agree with these observations and in addition predict that (i) inversion of Fano profiles is actually periodic in the coupling laser intensity and (ii) the supposedly dark $2p^2$ {$^1$S} state also appears in the spectrum. Closer inspection of the experimental data confirms the latter prediction.

arXiv:1211.2566Nov 12, 20122 citations

Coupling of autoionizing states by a chirped laser pulse

M. Žitnik, A. Mihelič, K. Bučar +11 more

Journal of Physics Conference SeriesJan 1, 20200 citations

Theoretical study of double-resonance processes in the helium continuum

Alessandro Lami, N. K. Rahman, Pietro Spizzo

The ionization spectrum of the He atom under double-resonance irradiation is studied theoretically. A previously developed theory is extended and adapted to treat this process. The first source (synchrotron) is tuned around the transition from the ground state to the 23sp-- $^{1}P^{o}$ autoionizing state, and the second source (laser) is put in resonance with the transition from 23sp-- $^{1}P^{o}$ to the higher-lying quasibound state 2p3p-- $^{1}P^{e}$ (or 2p4p, 2p5p). Accurate ab initio calculations have been performed to obtain all the necessary parameters. It is found that the single-field ionization spectrum is strongly modified, exhibiting coherent trapping and ac Stark splitting. These results are in consonance with previous model calculations as well as with other ab initio calculations on a different zone of the He continuum. The results show that for the resonances considered these strong effects can be observed at megawatt laser intensities.The ionization spectrum of the He atom under double-resonance irradiation is studied theoretically. A previously developed theory is extended and adapted to treat this process. The first source (synchrotron) is tuned around the transition from the ground state to the 23sp-- $^{1}P^{o}$ autoionizing state, and the second source (laser) is put in resonance with the transition from 23sp-- $^{1}P^{o}$ to the higher-lying quasibound state 2p3p-- $^{1}P^{e}$ (or 2p4p, 2p5p). Accurate ab initio calculations have been performed to obtain all the necessary parameters. It is found that the single-field ionization spectrum is strongly modified, exhibiting coherent trapping and ac Stark splitting. These results are in consonance with previous model calculations as well as with other ab initio calculations on a different zone of the He continuum. The results show that for the resonances considered these strong effects can be observed at megawatt laser intensities.

Physical Review ASep 1, 19897 citations

The strong coupling between two autoionizing states in helium is studied theoretically with the pump-probe scheme. An isolated 100-as XUV pulse is used to excite helium near the

2s2p{(}^{1}\phantom{\rule{0.16em}{0ex}}P)

resonance state in the presence of an intense infrared (IR) laser. The laser field introduces strong coupling between

2s2p{(}^{1}\phantom{\rule{0.16em}{0ex}}P)

and

2{p}^{2}{(}^{1}\phantom{\rule{0.16em}{0ex}}S)

states. The IR also can ionize helium from both autoionizing states. By changing the time delay between the XUV and the IR pulses, we investigated the photoelectron spectra near the two resonances. The results are used to explain the recent experiment by Gilbertson et al. [Phys. Rev. Lett. 105, 263003 (2010)]. Using the same isolated attosecond pulse and a 540-nm laser, we also investigate the strong coupling between

2s2p{(}^{1}\phantom{\rule{0.16em}{0ex}}P)

and

2{s}^{2}{(}^{1}\phantom{\rule{0.16em}{0ex}}S)

by examining how the photoelectron spectra are modified versus the time delay and the possibility of observing Autler-Townes doublet in such experiments.

2p^2

{

^1

S} state also appears in the spectrum. Closer inspection of the experimental data confirms the latter prediction.

^{1}P^{o}

autoionizing state, and the second source (laser) is put in resonance with the transition from 23sp--

^{1}P^{o}

to the higher-lying quasibound state 2p3p--

^{1}P^{e}

(or 2p4p, 2p5p). Accurate ab initio calculations have been performed to obtain all the necessary parameters. It is found that the single-field ionization spectrum is strongly modified, exhibiting coherent trapping and ac Stark splitting. These results are in consonance with previous model calculations as well as with other ab initio calculations on a different zone of the He continuum. The results show that for the resonances considered these strong effects can be observed at megawatt laser intensities.