Physical Review Letters

Polarization Dependence of Associative Ionization of Laser-Excited Na(3p)P322 Atoms

Joost Kircz, Reinhard Morgenstern, Gerard Nienhuis

Published Mar 1, 1982• 74 citations

Abstract

The associative ionization ${\mathrm{Na}}^{*}+{\mathrm{Na}}^{*}\ensuremath{\rightarrow}{{\mathrm{Na}}_{2}}^{+}+e$, when Na atoms in a single thermal beam are excited by linearly polarized light, was observed. The ion yield increases by a factor of 1.7 when the light polarization vector is rotated from a perpendicular to a parallel direction with respect to the beam. A theoretical analysis shows that the ionization rates $K$ obey the relations $K(\frac{1}{2}, \frac{3}{2})=0$ and $K(\frac{1}{2}, \frac{1}{2})=1.4K(\frac{3}{2}, \frac{3}{2})$, where the arguments indicate the initial magnetic substates $|{M}_{J}|$ of the two colliding atoms.

DOI: 10.1103/physrevlett.48.610

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Physical Review Letters

Polarization Dependence of Associative Ionization of Laser-Excited Na(3p)P322 Atoms

Joost Kircz, Reinhard Morgenstern, Gerard Nienhuis

Published Mar 1, 1982• 74 citations

Publisher

Abstract

The associative ionization

{\mathrm{Na}}^{*}+{\mathrm{Na}}^{*}\ensuremath{\rightarrow}{{\mathrm{Na}}_{2}}^{+}+e

, when Na atoms in a single thermal beam are excited by linearly polarized light, was observed. The ion yield increases by a factor of 1.7 when the light polarization vector is rotated from a perpendicular to a parallel direction with respect to the beam. A theoretical analysis shows that the ionization rates

K

obey the relations

K(\frac{1}{2}, \frac{3}{2})=0

and

K(\frac{1}{2}, \frac{1}{2})=1.4K(\frac{3}{2}, \frac{3}{2})

, where the arguments indicate the initial magnetic substates

|{M}_{J}|

of the two colliding atoms.

DOI: 10.1103/physrevlett.48.610

Related papers

Description of polarization-dependent associative ionization of radiatively excited atoms

Gerard Nienhuis

We analyze the dependence of the rate of associative ionization of two radiatively excited atoms on the polarization properties of the exciting light. This provides a direct relation between the observed ion-production rate as a function of the polarization and the ionization rates for various combinations of the magnetic substates. We consider an atomic beam irradiated by a single laser beam, as well as an atomic vapor. The description applies to a recent experimental observation of a strong polarization dependence of the ionization rate in an atomic beam, and at the same time we suggest alternate experimental methods of analyzing the total cross sections of any inelastic or reactive binary collision of excited atoms as a function of the magnetic quantum numbers.We analyze the dependence of the rate of associative ionization of two radiatively excited atoms on the polarization properties of the exciting light. This provides a direct relation between the observed ion-production rate as a function of the polarization and the ionization rates for various combinations of the magnetic substates. We consider an atomic beam irradiated by a single laser beam, as well as an atomic vapor. The description applies to a recent experimental observation of a strong polarization dependence of the ionization rate in an atomic beam, and at the same time we suggest alternate experimental methods of analyzing the total cross sections of any inelastic or reactive binary collision of excited atoms as a function of the magnetic quantum numbers.

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The authors have studied in a beam experiment the energy pooling reaction between two laser-excited Na* (3p) atoms, where in the final state one Na atom is in the 5s or 4d state and the other in the ground state. They have found that this reaction is strongly dependent on the polarization of the laser light used to prepare the Na*(3p) atoms. An analysis of theoretical potential curves suggests that the reaction mainly proceeds via the input channel where one of the atoms is in the M=0 and the other in the M=1 substate. Their experimental results are in qualitative agreement with that suggestion.The authors have studied in a beam experiment the energy pooling reaction between two laser-excited Na* (3p) atoms, where in the final state one Na atom is in the 5s or 4d state and the other in the ground state. They have found that this reaction is strongly dependent on the polarization of the laser light used to prepare the Na*(3p) atoms. An analysis of theoretical potential curves suggests that the reaction mainly proceeds via the input channel where one of the atoms is in the M=0 and the other in the M=1 substate. Their experimental results are in qualitative agreement with that suggestion.

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Dumont M. Jones, John S. Dahler

We consider collisions between (quasi-) one- or two-electron atoms, each of which has been prepared in a fixed distribution of hyperfine magnetic substates. The resulting ``polarization-dependent'' reaction rates are functions of (1) the (experimentally adjustable) orientation of the quantization axis associated with the hyperfine substates, (2) the hyperfine terms of the colliding atoms, and (3) the detailed reaction dynamics as characterized by preparation- and fine-structure-independent cross sections. These effects are deconvoluted and analyzed, and their use in elucidating reaction mechanisms is discussed. Particular emphasis is placed on the associative ionization of two Na(3p) atoms, each prepared by adsorption of resonant laser photons. The quasimolecular states of Na...Na that might react in this case are limited by selection rules. More information on the reaction mechanism is then obtained by using experimental data, in combination with the formal analysis, to draw further conclusions about the active quasimolecular states.We consider collisions between (quasi-) one- or two-electron atoms, each of which has been prepared in a fixed distribution of hyperfine magnetic substates. The resulting ``polarization-dependent'' reaction rates are functions of (1) the (experimentally adjustable) orientation of the quantization axis associated with the hyperfine substates, (2) the hyperfine terms of the colliding atoms, and (3) the detailed reaction dynamics as characterized by preparation- and fine-structure-independent cross sections. These effects are deconvoluted and analyzed, and their use in elucidating reaction mechanisms is discussed. Particular emphasis is placed on the associative ionization of two Na(3p) atoms, each prepared by adsorption of resonant laser photons. The quasimolecular states of Na...Na that might react in this case are limited by selection rules. More information on the reaction mechanism is then obtained by using experimental data, in combination with the formal analysis, to draw further conclusions about the active quasimolecular states.

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Harro A. J. Meijer, T. J. C. Pelgrim, H G M Heideman +2 more

We have investigated the associative ionization of Na atoms in two counterpropagating thermal beams independently excited by various combinations of linearly and circularly polarized light. In this way information about coherence contributions to the ion signal has been obtained for the first time. These contributions which correspond to off-diagonal elements of the detection matrix have hitherto been neglected, but are of the same magnitude as the cross sections themselves and depend on the velocity.We have investigated the associative ionization of Na atoms in two counterpropagating thermal beams independently excited by various combinations of linearly and circularly polarized light. In this way information about coherence contributions to the ion signal has been obtained for the first time. These contributions which correspond to off-diagonal elements of the detection matrix have hitherto been neglected, but are of the same magnitude as the cross sections themselves and depend on the velocity.

Physical Review LettersDec 28, 198720 citations

Ultracold photoassociative ionization collisions in an atomic beam: Optical field intensity and polarization dependence of the rate constant

Chun-Cheng Tsao, Reginaldo de Jesus Napolitano, Yang Wang +1 more

We report here measurements of two-body photoassociative ionization collisions between sodium atoms within an ultranarrow velocity class selected from a well-collimated, thermal atomic beam. Doppler-shifted excitation of the Na(3s ${\mathrm{}}^{2}$ ${\mathit{S}}_{1/2}$ ;F=1)\ensuremath{\rightarrow}Na(5p ${\mathrm{}}^{2}$ ${\mathit{P}}_{3/2}$ ) transition at 285 nm by a single-mode laser defines the narrow velocity class that subsequently populates the F=2 hyperfine level of the Na ground state by optical pumping. Probe laser beam excitation tuned near the Na(3s ${\mathrm{}}^{2}$ ${\mathit{S}}_{1/2}$ ;F=2)\ensuremath{\rightarrow}Na(3p ${\mathrm{}}^{2}$ ${\mathit{P}}_{3/2}$ ;F=3) transition produced photoassociative ionization with an average collision energy ${\mathit{E}}_{\mathit{K}}$ corresponding to a temperature of 5.3 mK ( ${\mathit{E}}_{\mathit{K}}$ =3/2kT). We determine the rate constant for the process as a function of probe beam intensity and polarization.We report here measurements of two-body photoassociative ionization collisions between sodium atoms within an ultranarrow velocity class selected from a well-collimated, thermal atomic beam. Doppler-shifted excitation of the Na(3s${\mathrm{}}^{2}$${\mathit{S}}_{1/2}$;F=1)\ensuremath{\rightarrow}Na(5p${\mathrm{}}^{2}$${\mathit{P}}_{3/2}$) transition at 285 nm by a single-mode laser defines the narrow velocity class that subsequently populates the F=2 hyperfine level of the Na ground state by optical pumping. Probe laser beam excitation tuned near the Na(3s${\mathrm{}}^{2}$${\mathit{S}}_{1/2}$;F=2)\ensuremath{\rightarrow}Na(3p${\mathrm{}}^{2}$${\mathit{P}}_{3/2}$;F=3) transition produced photoassociative ionization with an average collision energy ${\mathit{E}}_{\mathit{K}}$ corresponding to a temperature of 5.3 mK (${\mathit{E}}_{\mathit{K}}$=3/2kT). We determine the rate constant for the process as a function of probe beam intensity and polarization.

Physical Review AJan 1, 199511 citations

The associative ionization

{\mathrm{Na}}^{*}+{\mathrm{Na}}^{*}\ensuremath{\rightarrow}{{\mathrm{Na}}_{2}}^{+}+e

K

obey the relations

K(\frac{1}{2}, \frac{3}{2})=0

and

K(\frac{1}{2}, \frac{1}{2})=1.4K(\frac{3}{2}, \frac{3}{2})

, where the arguments indicate the initial magnetic substates

|{M}_{J}|

of the two colliding atoms.

{\mathrm{}}^{2}

{\mathit{S}}_{1/2}

;F=1)\ensuremath{\rightarrow}Na(5p

{\mathrm{}}^{2}

{\mathit{P}}_{3/2}

) transition at 285 nm by a single-mode laser defines the narrow velocity class that subsequently populates the F=2 hyperfine level of the Na ground state by optical pumping. Probe laser beam excitation tuned near the Na(3s

{\mathrm{}}^{2}

{\mathit{S}}_{1/2}

;F=2)\ensuremath{\rightarrow}Na(3p

{\mathrm{}}^{2}

{\mathit{P}}_{3/2}

;F=3) transition produced photoassociative ionization with an average collision energy

{\mathit{E}}_{\mathit{K}}

corresponding to a temperature of 5.3 mK (

{\mathit{E}}_{\mathit{K}}

=3/2kT). We determine the rate constant for the process as a function of probe beam intensity and polarization.