Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review Letters

Simultaneous Photoexcitation and Photoionization of Helium

James A. R. Samson

Published Apr 7, 1969• 69 citations
Publisher

Abstract

The probability of simultaneously photoexciting and photoionizing helium has been measured near threshold at a wavelength of 186 \AA{}. It was found that about (8 \ifmmode\pm\else\textpm\fi{} 2)% of the ions formed at that wavelength were excited into the $n=2$ state.

DOI
10.1103/physrevlett.22.693

Related papers

Two-color photoionization of helium above the N=2 ionization threshold

Thomas Grosges, Bernard Piraux, H. Bachau

We study two-color photoionization of helium in the region of the $3s3d{}^{1}D$ autoionizing state with resonant excitation of the intermediate $2s2p{}^{1}P$ autoionizing state. We show that the corresponding time-dependent Schr\"odinger equation may be solved by expanding the total wave function on a few complex energy states. Perimetric coordinates are used to describe correlation effects accurately. Populations at the end of the interaction as well as photoionization probabilities are studied as a function of the laser pulse duration and both frequencies. Our calculations show that many continua play a crucial role at high intensities.

Physical Review A•Aug 1, 1999•10 citations

Simultaneous electron-photon excitation of helium (h(cross) omega =1.17 eV)

S Luan, R. Hippler, Hans O. Lutz

The excitation of helium by the simultaneous impact of electrons and photons was investigated at a photon energy omega =1.17 eV. In the threshold region of the He (2s) excitation, the onset of the simultaneous process was observed; its threshold is significantly lower compared with the direct process without photon. At larger incident energies the measured signal disappears and eventually becomes negative. This is attributed to multiphoton ionization of metastable helium atoms.

Journal of Physics B Atomic Molecular and Optical Physics•Jul 28, 1991•47 citations

Doubly resonant photoionization of He below the N = 2 ionization threshold

A. Mihelič, M. Žitnik, Mateja Hrast

Abstract We present an extended theoretical study of two-colour doubly resonant photoionization of helium involving two doubly excited states below the N = 2 ionization threshold. We model the effects of a strong laser coupling between the lowest 1 P o and the selected 1 S e , 1 P e and 1 D e doubly excited states on the photoelectron (photoion) yield by taking into account the spatio-temporal structure of the pulses and by considering the effects of the neighbouring resonance states. We show that the laser coupling results in a measurable modification of the line profiles and in a reduction of the photoelectron yield under resonant or near-resonant conditions.

Journal of Physics B Atomic Molecular and Optical Physics•Oct 26, 2017•6 citations

Photoionization from the 5p 2P3/2 state of rubidium

Ali Nadeem, Sami Ul Haq

We report two-step photoionization studies from the 5$p$ ${}^{2}$${P}_{3/2}$ excited state of rubidium using two dye lasers simultaneously pumped by a common Nd:YAG laser in conjunction with a thermionic diode ion detector. The photoionization cross section at the first ionization threshold is measured as 18.8 \ifmmode\pm\else\textpm\fi{} 3 Mb and at excess energies of 0.013, 0.106, 0.229, and 0.329 eV is measured as 15, 13.6, 12.6, and 12.5 Mb, respectively. The measured value of the photoionization cross section at the threshold is used to calibrate the oscillator strengths of the 5$p$ ${}^{2}$${P}_{3/2}$ \ensuremath{\rightarrow} $n$d ${}^{2}$${D}_{5/2}$ (22 \ensuremath{\leqslant} $n$ \ensuremath{\leqslant} 52) Rydberg transitions.

Physical Review A•Jun 8, 2011•20 citations

Ionization of Rydberg atoms

Charles E. Burkhardt, Ron Corey, W. P. Garver +3 more

Ion formation in sodium vapor (\ensuremath{\sim}${10}^{11}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$) containing Rydberg atoms (18\ensuremath{\le}n\ensuremath{\le}35) was investigated. Both atomic ions and diatomic molecular ions resulting from collisions between highly excited sodium, ${\mathrm{Na}}^{\mathrm{*}\mathrm{*}}$, and Na(3s) were observed. However, the predominant production mechanism was found to be photoionization of ${\mathrm{Na}}^{\mathrm{*}\mathrm{*}}$ by blackbody radiation, the rate of which was measured at 500 K and found to be \ensuremath{\simeq}5.7\ifmmode\times\else\texttimes\fi{}${10}^{3}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ for n=18, in good agreement with theory. The ${\mathrm{Na}}^{+}$ signal from blackbody photoionization is observed to be independent of n, which we interpret as implying rapid and nearly complete self-l-mixing, mixing by collisions with Na(3s) atoms, for both s and d states. It is probable, however, that the s states are mixed to the adjacent, n-1, manifold of l states. It was also found that the heavy-body collision cross sections for ${\mathrm{Na}}^{+}$ and ${\mathrm{Na}}_{2}$${\mathrm{}}^{+}$ formation, while roughly three orders of magnitude lower than our estimate of the self-l-mixing cross section, are appreciable, of order 100 A${\r{}}^{2}$.

Physical Review A•Jul 1, 1986•28 citations

3C4 - Two-quantum photoionization of Cs and I-

J. L. Hall

This paper will review briefly a recent experiment which measured the photodetachment probability for I-ions due to simultaneous absorption of two ruby quanta. We have calculated the two-quantum photoionization rate for atomic cesium as a function of wavelength. The "transition" from the initial state to the bound intermediate state is expressed in terms of oscillator strengths. The second "transition," from these excited valence states into the coulomb continuum is expressed as a cross section. We have observed what appear to be genuine two-photon ionization signals in three cases: 1) near resonance in the10P_{3/2}state using the second-harmonic ofQ-switched ruby, 2) away from resonances, using the 5300 Å second-harmonic ofQ-switched neodymium laser, and 3) away from resonances using the first anti-Stokes line at 5750 Å from ruby-pumped D2gas. Present experiments aim at scanning the interesting range near resonance, e.g., by thermally tuning the ruby.

IEEE Journal of Quantum Electronics•Sep 1, 1966•23 citations
The probability of simultaneously photoexciting and photoionizing helium has been measured near threshold at a wavelength of 186 \AA{}. It was found that about (8 \ifmmode\pm\else\textpm\fi{} 2)% of the ions formed at that wavelength were excited into the n=2n=2n=2 state.
We study two-color photoionization of helium in the region of the 3s3d1D3s3d{}^{1}D3s3d1D autoionizing state with resonant excitation of the intermediate 2s2p1P2s2p{}^{1}P2s2p1P autoionizing state. We show that the corresponding time-dependent Schr\"odinger equation may be solved by expanding the total wave function on a few complex energy states. Perimetric coordinates are used to describe correlation effects accurately. Populations at the end of the interaction as well as photoionization probabilities are studied as a function of the laser pulse duration and both frequencies. Our calculations show that many continua play a crucial role at high intensities.
Abstract We present an extended theoretical study of two-colour doubly resonant photoionization of helium involving two doubly excited states below the N = 2 ionization threshold. We model the effects of a strong laser coupling between the lowest 1 P o and the selected 1 S e , 1 P e and 1 D e doubly excited states on the photoelectron (photoion) yield by taking into account the spatio-temporal structure of the pulses and by considering the effects of the neighbouring resonance states. We show that the laser coupling results in a measurable modification of the line profiles and in a reduction of the photoelectron yield under resonant or near-resonant conditions.
We report two-step photoionization studies from the 5ppp 2{}^{2}2P3/2{P}_{3/2}P3/2​ excited state of rubidium using two dye lasers simultaneously pumped by a common Nd:YAG laser in conjunction with a thermionic diode ion detector. The photoionization cross section at the first ionization threshold is measured as 18.8 \ifmmode\pm\else\textpm\fi{} 3 Mb and at excess energies of 0.013, 0.106, 0.229, and 0.329 eV is measured as 15, 13.6, 12.6, and 12.5 Mb, respectively. The measured value of the photoionization cross section at the threshold is used to calibrate the oscillator strengths of the 5ppp 2{}^{2}2P3/2{P}_{3/2}P3/2​ \ensuremath{\rightarrow} nnnd 2{}^{2}2D5/2{D}_{5/2}D5/2​ (22 \ensuremath{\leqslant} nnn \ensuremath{\leqslant} 52) Rydberg transitions.
Ion formation in sodium vapor (\ensuremath{\sim}1011{10}^{11}1011 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$) containing Rydberg atoms (18\ensuremath{\le}n\ensuremath{\le}35) was investigated. Both atomic ions and diatomic molecular ions resulting from collisions between highly excited sodium, Na∗∗{\mathrm{Na}}^{\mathrm{*}\mathrm{*}}Na∗∗, and Na(3s) were observed. However, the predominant production mechanism was found to be photoionization of Na∗∗{\mathrm{Na}}^{\mathrm{*}\mathrm{*}}Na∗∗ by blackbody radiation, the rate of which was measured at 500 K and found to be \ensuremath{\simeq}5.7\ifmmode\times\else\texttimes\fi{}103{10}^{3}103 ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ for n=18, in good agreement with theory. The Na+{\mathrm{Na}}^{+}Na+ signal from blackbody photoionization is observed to be independent of n, which we interpret as implying rapid and nearly complete self-l-mixing, mixing by collisions with Na(3s) atoms, for both s and d states. It is probable, however, that the s states are mixed to the adjacent, n-1, manifold of l states. It was also found that the heavy-body collision cross sections for Na+{\mathrm{Na}}^{+}Na+ and Na2{\mathrm{Na}}_{2}Na2​+{\mathrm{}}^{+}+ formation, while roughly three orders of magnitude lower than our estimate of the self-l-mixing cross section, are appreciable, of order 100 A˚2{\r{}}^{2}˚2.
This paper will review briefly a recent experiment which measured the photodetachment probability for I-ions due to simultaneous absorption of two ruby quanta. We have calculated the two-quantum photoionization rate for atomic cesium as a function of wavelength. The "transition" from the initial state to the bound intermediate state is expressed in terms of oscillator strengths. The second "transition," from these excited valence states into the coulomb continuum is expressed as a cross section. We have observed what appear to be genuine two-photon ionization signals in three cases: 1) near resonance in the10P_{3/2}state using the second-harmonic ofQ-switched ruby, 2) away from resonances, using the 5300 Å second-harmonic ofQ-switched neodymium laser, and 3) away from resonances using the first anti-Stokes line at 5750 Å from ruby-pumped D2gas. Present experiments aim at scanning the interesting range near resonance, e.g., by thermally tuning the ruby.