Physical Review A

Multiphoton ionization of cesium via quadrupole transitions: Photoelectron angular distributions and polarization effects on total ionization rates

A. Lyras, Bo-nian Dai, Xian Tang, P. Lambropoulos, Adila Dodhy, John A. D. Stockdale, Dino Zei, and R. N. Compton

Published Jan 1, 1988• 8 citations

Abstract

We report measurements of photoelectron angular distributions via electric quadrupole transitions in cesium atoms using multiphoton excitation techniques. Experimental results are presented for the cases of one-photon resonant, two-photon ionization via the 6d ${\mathrm{}}^{2}$${D}_{3/2}$ and 6d ${\mathrm{}}^{2}$${D}_{5/2}$ electric quadrupole transitions and for one-photon resonant, three-photon ionization via the 5d ${\mathrm{}}^{2}$ ${\mathrm{D}}_{3/2}$ and 5d ${\mathrm{}}^{2}$${D}_{5/2}$ transitions. The ratios of the total ionization rates for linearly and circularly polarized light have also been measured for the 6d ${\mathrm{}}^{2}$${\mathrm{D}}_{3/2}$ and 6d ${\mathrm{}}^{2}$${D}_{5/2}$ states. A theoretical analysis and detailed comparison with the experimental results are given.

DOI: 10.1103/physreva.37.403

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Physical Review A

Multiphoton ionization of cesium via quadrupole transitions: Photoelectron angular distributions and polarization effects on total ionization rates

A. Lyras, Bo-nian Dai, Xian Tang, P. Lambropoulos, Adila Dodhy, John A. D. Stockdale, Dino Zei, and R. N. Compton

Published Jan 1, 1988• 8 citations

Publisher

Abstract

{\mathrm{}}^{2}$${D}_{3/2}

and 6d

{\mathrm{}}^{2}$${D}_{5/2}

electric quadrupole transitions and for one-photon resonant, three-photon ionization via the 5d

{\mathrm{}}^{2}

{\mathrm{D}}_{3/2}

and 5d

{\mathrm{}}^{2}$${D}_{5/2}

transitions. The ratios of the total ionization rates for linearly and circularly polarized light have also been measured for the 6d

{\mathrm{}}^{2}$${\mathrm{D}}_{3/2}

and 6d

{\mathrm{}}^{2}$${D}_{5/2}

states. A theoretical analysis and detailed comparison with the experimental results are given.

DOI: 10.1103/physreva.37.403

Related papers

Near-infrared multiphoton ionization of cesium

William R. Christian, R. N. Compton, John A. D. Stockdale +4 more

Experimental and theoretical results are presented for resonantly enhanced three-photon ionization of cesium atoms in the wavelength range from 830 to 950 nm. The accidental near resonance of the $6p^{2}P_{\frac{3}{2},\frac{1}{2}}$ levels at the one-photon energy and the near resonance at the two-photon level with the $6d^{2}D_{\frac{3}{2},\frac{5}{2}}$ states gives rise to large ionization signals and interesting anomalies in the relative intensities of the fine-structure levels. "Hybrid resonances" are observed which involve the production of $6p ^{2}P_{\frac{1}{2}}$ atoms from molecular cesium. One hybrid resonance involves ionization of the $6p ^{2}P_{\frac{1}{2}}$ state via an electric quadrupole transition ($6p ^{2}P_{\frac{1}{2}}\ensuremath{-}7p ^{2}P_{\frac{3}{2}}$). Both experimental and theoretical photoelectron angular distributions are compared for all of the observed resonances except for the $6p ^{2}P_{\frac{3}{2}}$ state where the signals were too weak for such a measurement. Agreement between experiment and theory is fair for three-photon ionization via the $6p^{2}P_{\frac{1}{2}}$ state. Comparison of experiment and theory for the case of the $6d^{2}D_{\frac{3}{2},\frac{5}{2}}$ states indicates that hyperfine coupling during the laser-pulse duration may be important. The angular distributions for the hybrid resonances show the general behavior predicted by theory but the features appear broadened.Experimental and theoretical results are presented for resonantly enhanced three-photon ionization of cesium atoms in the wavelength range from 830 to 950 nm. The accidental near resonance of the $6p^{2}P_{\frac{3}{2},\frac{1}{2}}$ levels at the one-photon energy and the near resonance at the two-photon level with the $6d^{2}D_{\frac{3}{2},\frac{5}{2}}$ states gives rise to large ionization signals and interesting anomalies in the relative intensities of the fine-structure levels. "Hybrid resonances" are observed which involve the production of $6p ^{2}P_{\frac{1}{2}}$ atoms from molecular cesium. One hybrid resonance involves ionization of the $6p ^{2}P_{\frac{1}{2}}$ state via an electric quadrupole transition ($6p ^{2}P_{\frac{1}{2}}\ensuremath{-}7p ^{2}P_{\frac{3}{2}}$). Both experimental and theoretical photoelectron angular distributions are compared for all of the observed resonances except for the $6p ^{2}P_{\frac{3}{2}}$ state where the signals were too weak for such a measurement. Agreement between experiment and theory is fair for three-photon ionization via the $6p^{2}P_{\frac{1}{2}}$ state. Comparison of experiment and theory for the case of the $6d^{2}D_{\frac{3}{2},\frac{5}{2}}$ states indicates that hyperfine coupling during the laser-pulse duration may be important. The angular distributions for the hybrid resonances show the general behavior predicted by theory but the features appear broadened.

Physical Review AOct 1, 198411 citations

Photoelectron angular distributions from multiphoton ionization of cesium atoms

R. N. Compton, John A. D. Stockdale, C. Dewey Cooper +2 more

We present both experimental and theoretical studies of resonantly enhanced multiphoton ionization of cesium atoms. Photoelectron angular distributions for two-photon ionization via the one-photon-allowed $7p^{2}P_{\frac{1}{2},\frac{3}{2}}$ and $8p^{2}P_{\frac{1}{2},\frac{3}{2}}$ intermediate states and three-photon ionization via the two-photon-allowed $8d^{2}D_{\frac{5}{2},\frac{3}{2}}$ resonant intermediate states are reported. The photoelectrons are energy analyzed with a spherical-sector electrostatic energy analyzer with an energy resolution of ~ 0.1 eV and angular resolution of ~ \ifmmode\pm\else\textpm\fi{}2\ifmmode^\circ\else\textdegree\fi{}. A straightforward calculation based upon a finestructure scheme gives excellent agreement with the measured angular distributions for the $^{2}P_{\frac{1}{2}}$ states. The laser pulse duration is comparable to the hyperfine precession period which allows the hyperfine coupling to partially destroy the anisotropy initially produced in the $^{2}P_{\frac{3}{2}}$ resonant intermediate states. Quantitative calculations including hyperfine coupling take this into account and provide an expression which gives a reasonable fit to the $^{2}P_{\frac{3}{2}}$ data.We present both experimental and theoretical studies of resonantly enhanced multiphoton ionization of cesium atoms. Photoelectron angular distributions for two-photon ionization via the one-photon-allowed $7p^{2}P_{\frac{1}{2},\frac{3}{2}}$ and $8p^{2}P_{\frac{1}{2},\frac{3}{2}}$ intermediate states and three-photon ionization via the two-photon-allowed $8d^{2}D_{\frac{5}{2},\frac{3}{2}}$ resonant intermediate states are reported. The photoelectrons are energy analyzed with a spherical-sector electrostatic energy analyzer with an energy resolution of ~ 0.1 eV and angular resolution of ~ \ifmmode\pm\else\textpm\fi{}2\ifmmode^\circ\else\textdegree\fi{}. A straightforward calculation based upon a finestructure scheme gives excellent agreement with the measured angular distributions for the $^{2}P_{\frac{1}{2}}$ states. The laser pulse duration is comparable to the hyperfine precession period which allows the hyperfine coupling to partially destroy the anisotropy initially produced in the $^{2}P_{\frac{3}{2}}$ resonant intermediate states. Quantitative calculations including hyperfine coupling take this into account and provide an expression which gives a reasonable fit to the $^{2}P_{\frac{3}{2}}$ data.

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Multiphoton ionization of rubidium atoms near the 4d 2 D quadrupole transition

Adila Dodhy, R. N. Compton, John A. D. Stockdale

Photoelectron angular distributions have been measured for two-photon ionization of rubidium atoms both when the first photon was in resonance with the 4d ${\mathrm{}}^{2}$ D state via an electric quadrupole transition and when it was detuned from it. Angular distributions have also been obtained for the first and second above-threshold ionization (ATI) photoelectron peaks. Tuning to the 4d ${\mathrm{}}^{2}$ D resonance creates a large enhancement of the two-photon ionization photoelectron signal but causes only a modest increase in the ATI signal.Photoelectron angular distributions have been measured for two-photon ionization of rubidium atoms both when the first photon was in resonance with the 4d ${\mathrm{}}^{2}$D state via an electric quadrupole transition and when it was detuned from it. Angular distributions have also been obtained for the first and second above-threshold ionization (ATI) photoelectron peaks. Tuning to the 4d ${\mathrm{}}^{2}$D resonance creates a large enhancement of the two-photon ionization photoelectron signal but causes only a modest increase in the ATI signal.

Physical Review AMar 1, 198613 citations

The 6s-6d quadrupole resonances in two-photon ionisation of caesium. Measurement of ion asymmetry and spin polarisation

H Kaminski, Joachim Keßler, K J Kollath

In the two-photon ionisation of Cs atoms resonances may be expected which correspond to a quadrupole 6s-nd transition associated with the first photon. At the 6D 5/2 and 6D 3/2 resonances the ratio of photoionisation cross sections for circularly polarised and for linearly polarised light (ion asymmetry) and the spin polarisation of the photoelectrons ejected by circularly polarised light have been measured. The ratios of the radial transition matrix elements from the 6D to the epsilon P and epsilon F continuum states were derived from the experimental results.In the two-photon ionisation of Cs atoms resonances may be expected which correspond to a quadrupole 6s-nd transition associated with the first photon. At the 6D 5/2 and 6D 3/2 resonances the ratio of photoionisation cross sections for circularly polarised and for linearly polarised light (ion asymmetry) and the spin polarisation of the photoelectrons ejected by circularly polarised light have been measured. The ratios of the radial transition matrix elements from the 6D to the epsilon P and epsilon F continuum states were derived from the experimental results.

Journal of Physics B Atomic and Molecular PhysicsJul 14, 19799 citations

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Adila Dodhy, John A. D. Stockdale, R. N. Compton

AIP conference proceedingsJan 1, 19840 citations

Two-photon resonant three-photon ionization of the nd D2 states of cesium, rubidium, and sodium: Photoelectron angular distributions

Adila Dodhy, John A. D. Stockdale, R. N. Compton +3 more

Energy-resolved photoelectron angular distributions have been measured for the nd ${}^{2}$ D states (n=11--23) in cesium and rubidium atoms for two-photon resonant, three-photon ionization under conditions where the spin-orbit fine structure was not resolved. The photoelectron angular distributions reveal strong fine-structure mixing effects when the time duration of the laser pulse is longer than the time corresponding to the inverse of the fine-structure splitting of the nd states involved. Three-photon ionization photoelectron angular distributions for sodium atoms have been studied both experimentally and theoretically for laser frequencies in which resonance enhancement occurs via the two-photon excited nd ${}^{2}$ D states (n=5--9). The laser pulse duration is \ensuremath{\sim}6 ns which is comparable to or less than the fine-structure mixing time for the unperturbed fine-structure nd ${}^{2}$ ${D}_{5/2}$ ,3/2 levels. In addition, the high laser powers \ensuremath{\sim} ${10}^{8}$ W/ ${\mathrm{cm}}^{2}$ employed result in alterations of the energy separations of the fine-structure levels (and cause corresponding changes in the mixing times) due to the ac Stark effect. A detailed theoretical analysis is presented and good agreement is obtained with the experimental results.Energy-resolved photoelectron angular distributions have been measured for the nd ${}^{2}$D states (n=11--23) in cesium and rubidium atoms for two-photon resonant, three-photon ionization under conditions where the spin-orbit fine structure was not resolved. The photoelectron angular distributions reveal strong fine-structure mixing effects when the time duration of the laser pulse is longer than the time corresponding to the inverse of the fine-structure splitting of the nd states involved. Three-photon ionization photoelectron angular distributions for sodium atoms have been studied both experimentally and theoretically for laser frequencies in which resonance enhancement occurs via the two-photon excited nd ${}^{2}$D states (n=5--9). The laser pulse duration is \ensuremath{\sim}6 ns which is comparable to or less than the fine-structure mixing time for the unperturbed fine-structure nd ${}^{2}$${D}_{5/2}$,3/2 levels. In addition, the high laser powers \ensuremath{\sim}${10}^{8}$ W/${\mathrm{cm}}^{2}$ employed result in alterations of the energy separations of the fine-structure levels (and cause corresponding changes in the mixing times) due to the ac Stark effect. A detailed theoretical analysis is presented and good agreement is obtained with the experimental results.

Physical Review AApr 1, 19879 citations

{\mathrm{}}^{2}$${D}_{3/2}

and 6d

{\mathrm{}}^{2}$${D}_{5/2}

electric quadrupole transitions and for one-photon resonant, three-photon ionization via the 5d

{\mathrm{}}^{2}

{\mathrm{D}}_{3/2}

and 5d

{\mathrm{}}^{2}$${D}_{5/2}

transitions. The ratios of the total ionization rates for linearly and circularly polarized light have also been measured for the 6d

{\mathrm{}}^{2}$${\mathrm{D}}_{3/2}

and 6d

{\mathrm{}}^{2}$${D}_{5/2}

states. A theoretical analysis and detailed comparison with the experimental results are given.

Experimental and theoretical results are presented for resonantly enhanced three-photon ionization of cesium atoms in the wavelength range from 830 to 950 nm. The accidental near resonance of the

6p^{2}P_{\frac{3}{2},\frac{1}{2}}

levels at the one-photon energy and the near resonance at the two-photon level with the

6d^{2}D_{\frac{3}{2},\frac{5}{2}}

states gives rise to large ionization signals and interesting anomalies in the relative intensities of the fine-structure levels. "Hybrid resonances" are observed which involve the production of

6p ^{2}P_{\frac{1}{2}}

atoms from molecular cesium. One hybrid resonance involves ionization of the

6p ^{2}P_{\frac{1}{2}}

state via an electric quadrupole transition ($6p ^{2}P_{\frac{1}{2}}\ensuremath{-}7p ^{2}P_{\frac{3}{2}}$). Both experimental and theoretical photoelectron angular distributions are compared for all of the observed resonances except for the

6p ^{2}P_{\frac{3}{2}}

state where the signals were too weak for such a measurement. Agreement between experiment and theory is fair for three-photon ionization via the

6p^{2}P_{\frac{1}{2}}

state. Comparison of experiment and theory for the case of the

6d^{2}D_{\frac{3}{2},\frac{5}{2}}

states indicates that hyperfine coupling during the laser-pulse duration may be important. The angular distributions for the hybrid resonances show the general behavior predicted by theory but the features appear broadened.

7p^{2}P_{\frac{1}{2},\frac{3}{2}}

and

8p^{2}P_{\frac{1}{2},\frac{3}{2}}

intermediate states and three-photon ionization via the two-photon-allowed

8d^{2}D_{\frac{5}{2},\frac{3}{2}}

resonant intermediate states are reported. The photoelectrons are energy analyzed with a spherical-sector electrostatic energy analyzer with an energy resolution of ~ 0.1 eV and angular resolution of ~ \ifmmode\pm\else\textpm\fi{}2\ifmmode^\circ\else\textdegree\fi{}. A straightforward calculation based upon a finestructure scheme gives excellent agreement with the measured angular distributions for the

^{2}P_{\frac{1}{2}}

states. The laser pulse duration is comparable to the hyperfine precession period which allows the hyperfine coupling to partially destroy the anisotropy initially produced in the

^{2}P_{\frac{3}{2}}

resonant intermediate states. Quantitative calculations including hyperfine coupling take this into account and provide an expression which gives a reasonable fit to the

^{2}P_{\frac{3}{2}}

data.

Photoelectron angular distributions have been measured for two-photon ionization of rubidium atoms both when the first photon was in resonance with the 4d

{\mathrm{}}^{2}

D state via an electric quadrupole transition and when it was detuned from it. Angular distributions have also been obtained for the first and second above-threshold ionization (ATI) photoelectron peaks. Tuning to the 4d

{\mathrm{}}^{2}

D resonance creates a large enhancement of the two-photon ionization photoelectron signal but causes only a modest increase in the ATI signal.

Energy-resolved photoelectron angular distributions have been measured for the nd

{}^{2}

D states (n=11--23) in cesium and rubidium atoms for two-photon resonant, three-photon ionization under conditions where the spin-orbit fine structure was not resolved. The photoelectron angular distributions reveal strong fine-structure mixing effects when the time duration of the laser pulse is longer than the time corresponding to the inverse of the fine-structure splitting of the nd states involved. Three-photon ionization photoelectron angular distributions for sodium atoms have been studied both experimentally and theoretically for laser frequencies in which resonance enhancement occurs via the two-photon excited nd

{}^{2}

D states (n=5--9). The laser pulse duration is \ensuremath{\sim}6 ns which is comparable to or less than the fine-structure mixing time for the unperturbed fine-structure nd

{}^{2}

{D}_{5/2}

,3/2 levels. In addition, the high laser powers \ensuremath{\sim}

{10}^{8}

{\mathrm{cm}}^{2}

employed result in alterations of the energy separations of the fine-structure levels (and cause corresponding changes in the mixing times) due to the ac Stark effect. A detailed theoretical analysis is presented and good agreement is obtained with the experimental results.