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

Journal of Physics B Atomic and Molecular Physics

Pulse strength and pulse duration effect on photoelectron polarisation in resonant two-photon ionisation

R. Parzyński

Published Dec 28, 1984• 1 citation
Publisher

Abstract

Polarisation of photoelectrons produced from unpolarised alkali atoms is studied analytically for a wide range of the strengths and durations of the light pulse. In the particular case of long pulse durations, where the rate equation for the ionisation probability is approached, the photoelectron polarisation is shown to be a monotonically decreasing function of the pulse strength. In the case of weak pulses, usually dealt with by perturbation theory, the photoelectron polarisation is found to decrease continuously when the pulse duration is shortened. It is, however, found also that if neither the long pulse duration or the weak-field condition is fulfilled then an increase in pulse strength and a shortening of the pulse duration need not always affect the photoelectron polarisation destructively.

DOI
10.1088/0022-3700/17/24/023

Related papers

Photoelectron polarisation in resonant two-photon ionisation with superstrong continuous excitation

R. Parzyński

Non-perturbative completely analytic calculations of the spin polarisation of photoelectrons produced in resonant two-photon ionisation of alkali atoms with exciting and ionising light beams are presented. A well justified alkali atom model composed of four discrete states and the continuum is applied. Contrary to simpler models it enabled one to obtain results valid when the effective resonance Rabi frequency exceeds the frequency separation between the two components forming a given fine-structure energy doublet at resonance. It is shown that in this limit the photoelectron polarisation depends critically on whether a light or heavy alkali atom is ionised. In the former case the photoelectron polarisation is proved to be a copy of the electronic polarisation of the atom, whereas in the case of heavier alkalis it departs appreciably from that of the ionised atom due entirely to spin-orbit perturbation of radial wavefunctions of P discrete states. It is also shown how the author's present results go over into those previously obtained for weaker exciting fields.

Journal of Physics B Atomic and Molecular Physics•Dec 28, 1983•2 citations

Photoelectron polarisation in two-photon ionisation with two different light beams

R. Parzyński

A new formula is proposed for the spin-polarisation degree of photoelectrons, emitted from the ground state of alkali atoms in two-photon ionisation caused by two different light beams. The formula is derived within the fine structure scheme and can be applied to polarised as well as unpolarised atoms, all conceivable experimental geometries, all possible combinations of polarisation states of the exciting and ionising light beams, and for near-resonance with a P doublet intermediate state.

Journal of Physics B Atomic and Molecular Physics•Feb 14, 1980•10 citations

Formalism for two-photon ionisation of alkali atoms via a resonant intermediate state

G Nienhius, Ernst H.A. Granneman, Marnix J. van der Wiel

A density-matrix formulation is given of two-photon ionisation of alkali atoms, for two incoming light pulses of arbitrary direction, polarisation, pulse duration and time difference. The frequency of one of the pulses coincides with a resonant transition. The emphasis is on separating out angular momentum factors from the basic physics contained in the radial matrix elements of the atomic electric dipole. The bandwidth of the exciting light is assumed large compared to natural and induced linewidths. The polarisation of the photoelectron is calculated with or without saturation of the excitation for various values of the nuclear spin.

Journal of Physics B Atomic and Molecular Physics•Apr 14, 1978•27 citations

Angular distributions and polarisation phenomena in non-resonant multiphoton ionisation of alkali-metal atoms. II. Two-photon ionisation of atomic caesium

G Laplanche, M. Jaouen, A. Rachman

For pt.I see ibid., vol.19, p.79 (1986). The authors study the two-photon ionisation of unpolarised target atoms of caesium in their ground state or in one of the two first excited states 6P 1/2 or 6P 3/2 in the non-resonant region. Circularly, linearly and unpolarised light are considered. For each case they give a systematic analysis of generalised transition probabilities, angular distributions and polarisation phenomena. In particular, it is shown that polarised electrons can be obtained even with linearly or unpolarised light.

Journal of Physics B Atomic and Molecular Physics•Jan 14, 1986•3 citations

Time development of resonant multiphoton ionisation of sodium

Stanley L. Haan, S. Geltman

The time evolution of the ionisation probability of a sodium atom irradiated by linearly polarised light with frequency near the 3s-3p transition frequency is studied theoretically by the following method. The 3s and 3p states are strongly coupled using the rotating-wave approximation and then the resulting strongly coupled wavefunction is used as the lowest-order approximation in applying second-order perturbation theory to obtain the ionisation probability. The photoelectron energy spectrum and total ionisation probability are studied for various laser detunings and turn-on forms. Processes which are forbidden at long times by energy conservation are found to be important at short times (t<or approximately=10 -9 s for a laser intensity of order MW cm -2 ) . The ionisation probability is found to exhibit a plateau behaviour at times much less than the 3s-3p Rabi cycling time and subsequently to oscillate with the 3p population before reaching rate behaviour in the long-time limit.

Journal of Physics B Atomic and Molecular Physics•Apr 28, 1982•14 citations

Polarised electrons and two-photon-resonant ionisation of unpolarised atoms

A I Andrjushin, Alexey E. Kazakov

General expressions are presented and investigated for the degree of polarisation of electrons produced in the resonant two-photon ionisation of unpolarised atoms from the ground S state. The exciting and ionising electromagnetic fields are assumed to have arbitrary directions of propagation and arbitrary degrees of polarisation. It is shown that completely polarised electrons can be obtained when the matrix element of the P to S transition from the resonant state to the continuum is larger than the matrix element of the P to D transition. Such cases are realised in sodium and potassium atoms.

Journal of Physics B Atomic and Molecular Physics•Oct 28, 1980•2 citations
Polarisation of photoelectrons produced from unpolarised alkali atoms is studied analytically for a wide range of the strengths and durations of the light pulse. In the particular case of long pulse durations, where the rate equation for the ionisation probability is approached, the photoelectron polarisation is shown to be a monotonically decreasing function of the pulse strength. In the case of weak pulses, usually dealt with by perturbation theory, the photoelectron polarisation is found to decrease continuously when the pulse duration is shortened. It is, however, found also that if neither the long pulse duration or the weak-field condition is fulfilled then an increase in pulse strength and a shortening of the pulse duration need not always affect the photoelectron polarisation destructively.
Non-perturbative completely analytic calculations of the spin polarisation of photoelectrons produced in resonant two-photon ionisation of alkali atoms with exciting and ionising light beams are presented. A well justified alkali atom model composed of four discrete states and the continuum is applied. Contrary to simpler models it enabled one to obtain results valid when the effective resonance Rabi frequency exceeds the frequency separation between the two components forming a given fine-structure energy doublet at resonance. It is shown that in this limit the photoelectron polarisation depends critically on whether a light or heavy alkali atom is ionised. In the former case the photoelectron polarisation is proved to be a copy of the electronic polarisation of the atom, whereas in the case of heavier alkalis it departs appreciably from that of the ionised atom due entirely to spin-orbit perturbation of radial wavefunctions of P discrete states. It is also shown how the author's present results go over into those previously obtained for weaker exciting fields.
A density-matrix formulation is given of two-photon ionisation of alkali atoms, for two incoming light pulses of arbitrary direction, polarisation, pulse duration and time difference. The frequency of one of the pulses coincides with a resonant transition. The emphasis is on separating out angular momentum factors from the basic physics contained in the radial matrix elements of the atomic electric dipole. The bandwidth of the exciting light is assumed large compared to natural and induced linewidths. The polarisation of the photoelectron is calculated with or without saturation of the excitation for various values of the nuclear spin.
For pt.I see ibid., vol.19, p.79 (1986). The authors study the two-photon ionisation of unpolarised target atoms of caesium in their ground state or in one of the two first excited states 6P 1/2 or 6P 3/2 in the non-resonant region. Circularly, linearly and unpolarised light are considered. For each case they give a systematic analysis of generalised transition probabilities, angular distributions and polarisation phenomena. In particular, it is shown that polarised electrons can be obtained even with linearly or unpolarised light.
The time evolution of the ionisation probability of a sodium atom irradiated by linearly polarised light with frequency near the 3s-3p transition frequency is studied theoretically by the following method. The 3s and 3p states are strongly coupled using the rotating-wave approximation and then the resulting strongly coupled wavefunction is used as the lowest-order approximation in applying second-order perturbation theory to obtain the ionisation probability. The photoelectron energy spectrum and total ionisation probability are studied for various laser detunings and turn-on forms. Processes which are forbidden at long times by energy conservation are found to be important at short times (t<or approximately=10 -9 s for a laser intensity of order MW cm -2 ) . The ionisation probability is found to exhibit a plateau behaviour at times much less than the 3s-3p Rabi cycling time and subsequently to oscillate with the 3p population before reaching rate behaviour in the long-time limit.
General expressions are presented and investigated for the degree of polarisation of electrons produced in the resonant two-photon ionisation of unpolarised atoms from the ground S state. The exciting and ionising electromagnetic fields are assumed to have arbitrary directions of propagation and arbitrary degrees of polarisation. It is shown that completely polarised electrons can be obtained when the matrix element of the P to S transition from the resonant state to the continuum is larger than the matrix element of the P to D transition. Such cases are realised in sodium and potassium atoms.