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

Resonance two-photon ionisation with ultrashort laser pulses

Davıd L. Andrews

Published Dec 1, 1977• 17 citations
Publisher

Abstract

An expression is derived for the amount of two-photon ionisation produced by sub-nanosecond laser pulses under resonance conditions. On this time scale damping effects can be neglected and the ionisation probability becomes proportional to the cube of the pulse duration. A similar prediction for resonance multiphoton processes of higher order leads to a qualitative agreement with recent experimental observations. Finally, it is demonstrated that the same result can be obtained from a simple analysis of a two-step model.

DOI
10.1088/0022-3700/10/17/004

Related papers

Raman-type resonances in two-laser multiphoton ionisation

R. Parzyński

Higher-order multiphoton ionisation enhanced resonantly by Raman-type transitions is studied theoretically. This higher-order process is found to be stronger than the non-resonant lowest-order one by approximately two orders of magnitude. The shape, position, width, height and area of the resonance peaks that appear due to this process are calculated. Qualitative agreement is found between the theory and the experiment of Feldmann et al. (1986).

Journal of Physics B Atomic and Molecular Physics•Jan 14, 1987•5 citations

Theory of N-photon ionisation with short laser pulses

W A McClean, S. Swain

An expression for the N-photon ionisation probability for a many-level atom is obtained as a function of the laser pulse duration, t. It is shown that the leading term in the power series expansion is of order t 2N-1 . The relevance of these calculations to some recent experiments by Lompre et al. (1976, 1977) is discussed.

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

Spatio-temporal effects in resonant multiphoton ionisation of the caesium atom

Yves Gontier, M. Trahin

The time evolution of a resonance peak is studied for three- and four-photon ionisation of the caesium atom with square and Gaussian laser pulses. In the domain 10 -13 -10 -7 s two different regimes are defined according to whether the time is smaller or larger than a characteristic time t c . For t<t c the ionisation probability varies as t 3 whereas it is proportional to t when t>t c . The corresponding resonance width varies as t -1 in the first case becomes intensity independent in the second. The effects of the spatial distribution of the intensity in the focal volume are discussed and an excellent agreement is found between the theoretical and experimental values of the order of non-linearity, the resonance width and the absolute magnitude of the ion signal.

Journal of Physics B Atomic and Molecular Physics•Jan 28, 1980•26 citations

The time dependence of two-phonon ionisation

W A McClean, S. Swain

The authors treat a model for photoionisation in which the atom has many bound atomic levels and the laser may be either monochromatic or possess a finite bandwidth. The treatment is restricted to the case where the laser is not sufficiently intense to cause Stark splitting of the atomic energy levels. They obtain an expression for the two-photon ionisation probability as a function of time which covers both resonant and non-resonant excitation. They identify several time regimes where the probability takes on a particularly simple form. In particular they discuss the short time behaviour and the conditions under which a time-independent transition rate exists. Numerical plots of the ionisation probability against laser frequency for a wide range of pulse durations are given for the two-level model.

Journal of Physics B Atomic and Molecular Physics•Jul 28, 1979•13 citations

The influence of radiative collisions on two-photon atomic ionisation

Michele Crance, S. Feneuille

Investigates theoretically a new aspect of radiative collisions on two-photon ionisation of colliding atoms of different species A and B. The authors derive the main characteristics of the resonance appearing in the two-photon ionisation cross section of atom B when the laser frequency is tuned on a resonance transition of atom A which cannot itself be ionised by two-photon absorption. Under some realistic conditions and for reasonable values of the light energy density flux F ( approximately 1 MW cm -2 ), the cross section of the process considered varies as F 2/5 while its width varies as F 1/2 . These predictions are in reasonable agreement with a recent observation on the mixture Sr(A)-Cs(B) by Brechignac et al. (1980).

Journal of Physics B Atomic and Molecular Physics•Aug 28, 1980•7 citations

A simple model for multiphoton ionisation

S. Swain

The author examines some simple models for multiphoton ionisation which can be constructed when the bound-free transition rates are much smaller than the bound-bound transition rates and considers how to proceed when this condition is relaxed. The author identifies a regime where the transition rate is time independent. If the laser has a sufficiently broad linewidth one can use a rate equation approach; this assertion is justified and applied to two-, three- and N-photon ionisation. If the laser is narrow-band, a density matrix method has to be used and the effects of different laser lineshapes are discussed. In three-photon ionisation the role of optical pumping effects is emphasised. Explicit expressions for the multiphoton ionisation probabilities are presented and finally some extensions of the method are briefly discussed.

Journal of Physics B Atomic and Molecular Physics•Oct 14, 1979•23 citations
An expression is derived for the amount of two-photon ionisation produced by sub-nanosecond laser pulses under resonance conditions. On this time scale damping effects can be neglected and the ionisation probability becomes proportional to the cube of the pulse duration. A similar prediction for resonance multiphoton processes of higher order leads to a qualitative agreement with recent experimental observations. Finally, it is demonstrated that the same result can be obtained from a simple analysis of a two-step model.
The time evolution of a resonance peak is studied for three- and four-photon ionisation of the caesium atom with square and Gaussian laser pulses. In the domain 10 -13 -10 -7 s two different regimes are defined according to whether the time is smaller or larger than a characteristic time t c . For t<t c the ionisation probability varies as t 3 whereas it is proportional to t when t>t c . The corresponding resonance width varies as t -1 in the first case becomes intensity independent in the second. The effects of the spatial distribution of the intensity in the focal volume are discussed and an excellent agreement is found between the theoretical and experimental values of the order of non-linearity, the resonance width and the absolute magnitude of the ion signal.
The authors treat a model for photoionisation in which the atom has many bound atomic levels and the laser may be either monochromatic or possess a finite bandwidth. The treatment is restricted to the case where the laser is not sufficiently intense to cause Stark splitting of the atomic energy levels. They obtain an expression for the two-photon ionisation probability as a function of time which covers both resonant and non-resonant excitation. They identify several time regimes where the probability takes on a particularly simple form. In particular they discuss the short time behaviour and the conditions under which a time-independent transition rate exists. Numerical plots of the ionisation probability against laser frequency for a wide range of pulse durations are given for the two-level model.
Investigates theoretically a new aspect of radiative collisions on two-photon ionisation of colliding atoms of different species A and B. The authors derive the main characteristics of the resonance appearing in the two-photon ionisation cross section of atom B when the laser frequency is tuned on a resonance transition of atom A which cannot itself be ionised by two-photon absorption. Under some realistic conditions and for reasonable values of the light energy density flux F ( approximately 1 MW cm -2 ), the cross section of the process considered varies as F 2/5 while its width varies as F 1/2 . These predictions are in reasonable agreement with a recent observation on the mixture Sr(A)-Cs(B) by Brechignac et al. (1980).
The author examines some simple models for multiphoton ionisation which can be constructed when the bound-free transition rates are much smaller than the bound-bound transition rates and considers how to proceed when this condition is relaxed. The author identifies a regime where the transition rate is time independent. If the laser has a sufficiently broad linewidth one can use a rate equation approach; this assertion is justified and applied to two-, three- and N-photon ionisation. If the laser is narrow-band, a density matrix method has to be used and the effects of different laser lineshapes are discussed. In three-photon ionisation the role of optical pumping effects is emphasised. Explicit expressions for the multiphoton ionisation probabilities are presented and finally some extensions of the method are briefly discussed.