Topical Meeting on Laser Techniques in the Extreme Ultraviolet

Multiphoton Ionization of Cesium Atoms Above and Below The Two-Photon Ionization Threshold

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

Published Jan 1, 1984• 0 citations

Abstract

The experimental arrangement consisted of a Nd:YAG pumped pulsed dye laser which was focused and crossed at right angle with a cesium beam. Photoelectrons were energy-analyzed by a spherical sector energy analyzer and detected with a dual multichannel plate.

DOI: 10.1364/euv.1984.mc2

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Multiphoton ionization of cesium atoms above and below the two-photon ionization threshold

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Topical Meeting on Laser Techniques in the Extreme Ultraviolet

Multiphoton Ionization of Cesium Atoms Above and Below The Two-Photon Ionization Threshold

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

Published Jan 1, 1984• 0 citations

Publisher

Abstract

DOI: 10.1364/euv.1984.mc2

Related papers

Multiphoton ionization of cesium atoms above and below the two-photon ionization threshold

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

AIP conference proceedingsJan 1, 19840 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 (MPI) spectra of sodium and cesium were obtained in a crossed $N_{2}$ pumped dye laser and alkali beam. Hybrid resonance were observed at the cesium $7d^{2}D_{3/2} -6p^{2}P_{1/2}$ and $7p^{2}P_{3/2}- 6p^{2}P_{1/2}$ transitions and the sodium $4d^{2}D_{3/2, 5/2} - 3p^{2}P_{1/2, 3/2}$ transitions together with the more common MPI via intermediate S, P and D states. Power dependences for these processes are presented together with and interesting case of a switch from red to blue Stark shifting in the sodium MPI spectrum.Multiphoton ionization (MPI) spectra of sodium and cesium were obtained in a crossed $N_{2}$ pumped dye laser and alkali beam. Hybrid resonance were observed at the cesium $7d^{2}D_{3/2} -6p^{2}P_{1/2}$ and $7p^{2}P_{3/2}- 6p^{2}P_{1/2}$ transitions and the sodium $4d^{2}D_{3/2, 5/2} - 3p^{2}P_{1/2, 3/2}$ transitions together with the more common MPI via intermediate S, P and D states. Power dependences for these processes are presented together with and interesting case of a switch from red to blue Stark shifting in the sodium MPI spectrum.

Jan 1, 19820 citations

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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.

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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.

Multiphoton ionization (MPI) spectra of sodium and cesium were obtained in a crossed

N_{2}

pumped dye laser and alkali beam. Hybrid resonance were observed at the cesium

7d^{2}D_{3/2} -6p^{2}P_{1/2}

and

7p^{2}P_{3/2}- 6p^{2}P_{1/2}

transitions and the sodium

4d^{2}D_{3/2, 5/2} - 3p^{2}P_{1/2, 3/2}

transitions together with the more common MPI via intermediate S, P and D states. Power dependences for these processes are presented together with and interesting case of a switch from red to blue Stark shifting in the sodium MPI spectrum.

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.