Physical Review A

Description of polarization-dependent associative ionization of radiatively excited atoms

Gerard Nienhuis

Published Dec 1, 1982• 44 citations

Abstract

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.

DOI: 10.1103/physreva.26.3137

Related papers

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

Joost Kircz, Reinhard Morgenstern, Gerard Nienhuis

Physical Review LettersMar 1, 198274 citations

Associative ionization in collisions between excited Na atoms in the and the states

Jan Jette Blange, G Aben, H. Rudolph +2 more

Journal of Physics B Atomic Molecular and Optical PhysicsJun 28, 19972 citations

Theory of the polarization dependence of reactive collisions and its application to the associative ionization process 2Na(3 P3/22 )→ Na2 + (X 2 Σg+ )+ e−

Dumont M. Jones, John S. Dahler

Physical Review AMay 1, 198716 citations

The use of weak magnetic fields in collisions of polarized atoms

Harro A. J. Meijer, Th. Zeegers, T. J. C. Pelgrim +2 more

The Journal of Chemical PhysicsJan 15, 198911 citations

Polarization-dependent photoionization cross sections and radiative lifetimes of atomic states in BaI

C.-H. Li, Dmitry Budker

arXiv:physics/0602189Physical Review AJul 31, 20067 citations

Cold collisions in an atomic beam

H. R. Thorsheim, Yanping Wang, J. Weiner

Physical Review AMar 1, 199025 citations

Physical Review A

Description of polarization-dependent associative ionization of radiatively excited atoms

Gerard Nienhuis

Published Dec 1, 1982• 44 citations

Publisher

Abstract

DOI: 10.1103/physreva.26.3137

Related papers

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

Joost Kircz, Reinhard Morgenstern, Gerard Nienhuis

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.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.

Physical Review LettersMar 1, 198274 citations

Associative ionization in collisions between excited Na atoms in the and the states

Jan Jette Blange, G Aben, H. Rudolph +2 more

For the first time, associative ionization has been observed in an atomic beam of excited sodium atoms in both the and the state. Relative values for the partial cross sections were obtained specified according to the different magnetic substate combinations of the two fine-structure states. These were found to be comparable to those for associative ionization between two atoms. However, the effect of the excitation on the ion production rate was found to be considerable and to depend strongly on the relative polarizations of the laser beams producing the two populations due to the redistribution of the involved magnetic sublevels. The results indicate that the initial orientation of the electron spin S does not significantly influence the associative ionization reaction at the mean collision energy of 25 meV.For the first time, associative ionization has been observed in an atomic beam of excited sodium atoms in both the and the state. Relative values for the partial cross sections were obtained specified according to the different magnetic substate combinations of the two fine-structure states. These were found to be comparable to those for associative ionization between two atoms. However, the effect of the excitation on the ion production rate was found to be considerable and to depend strongly on the relative polarizations of the laser beams producing the two populations due to the redistribution of the involved magnetic sublevels. The results indicate that the initial orientation of the electron spin S does not significantly influence the associative ionization reaction at the mean collision energy of 25 meV.

Journal of Physics B Atomic Molecular and Optical PhysicsJun 28, 19972 citations

Theory of the polarization dependence of reactive collisions and its application to the associative ionization process 2Na(3 P3/22 )→ Na2 + (X 2 Σg+ )+ e−

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.

Physical Review AMay 1, 198716 citations

The use of weak magnetic fields in collisions of polarized atoms

Harro A. J. Meijer, Th. Zeegers, T. J. C. Pelgrim +2 more

We have experimentally and theoretically investigated the behavior of excited Na atoms under the combined influence of resonant laser light and a weak magnetic field. The use of weak magnetic fields gives another possibility to vary the polarization of the atoms, additional to variation of the polarization of the exciting laser. We calculated in detail the influence of weak magnetic fields on the density matrix describing the excited atoms, using generalized rate equations. We checked the results of our model experimentally, at the Na(3 2 S1/2, Fl=2) →(3 2 P3/2, Fu =3) transition, excited with circularly polarized light. We determined the polarization of the excited atoms, by measuring the fluorescence light at various angles, as a function of both magnetic field strength and laser irradiance. Model and experiment agreed very well. We applied our model to the associative ionization of the excited Na atoms. We measured the ion signal as a function of magnetic field. Analyzing the results, we could determine a specific associative ionization cross section, which is not accessible in our experimental geometry without the use of magnetic fields. Thereby we showed that the application of magnetic fields in polarization dependence studies can provide us with additional information about the process.We have experimentally and theoretically investigated the behavior of excited Na atoms under the combined influence of resonant laser light and a weak magnetic field. The use of weak magnetic fields gives another possibility to vary the polarization of the atoms, additional to variation of the polarization of the exciting laser. We calculated in detail the influence of weak magnetic fields on the density matrix describing the excited atoms, using generalized rate equations. We checked the results of our model experimentally, at the Na(3 2 S1/2, Fl=2) →(3 2 P3/2, Fu =3) transition, excited with circularly polarized light. We determined the polarization of the excited atoms, by measuring the fluorescence light at various angles, as a function of both magnetic field strength and laser irradiance. Model and experiment agreed very well. We applied our model to the associative ionization of the excited Na atoms. We measured the ion signal as a function of magnetic field. Analyzing the results, we could determine a specific associative ionization cross section, which is not accessible in our experimental geometry without the use of magnetic fields. Thereby we showed that the application of magnetic fields in polarization dependence studies can provide us with additional information about the process.

The Journal of Chemical PhysicsJan 15, 198911 citations

Polarization-dependent photoionization cross sections and radiative lifetimes of atomic states in BaI

C.-H. Li, Dmitry Budker

The photoionization cross sections of two even-parity excited states $5d6d\phantom{\rule{0.3em}{0ex}}^{3}D_{1}$ and $6s7d\phantom{\rule{0.3em}{0ex}}^{3}D_{2}$ of atomic Ba at the ionization-laser wavelength of $556.6\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ were measured. We found that the total cross section depends on the relative polarization of the atoms and the ionization-laser light. With density-matrix algebra, we show that, in general, there are at most three parameters in the photoionization cross section. Some of these parameters are determined in this work. We also present the measurement of the radiative lifetime of five even-parity excited states of barium.The photoionization cross sections of two even-parity excited states $5d6d\phantom{\rule{0.3em}{0ex}}^{3}D_{1}$ and $6s7d\phantom{\rule{0.3em}{0ex}}^{3}D_{2}$ of atomic Ba at the ionization-laser wavelength of $556.6\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ were measured. We found that the total cross section depends on the relative polarization of the atoms and the ionization-laser light. With density-matrix algebra, we show that, in general, there are at most three parameters in the photoionization cross section. Some of these parameters are determined in this work. We also present the measurement of the radiative lifetime of five even-parity excited states of barium.

arXiv:physics/0602189Physical Review AJul 31, 20067 citations

Cold collisions in an atomic beam

H. R. Thorsheim, Yanping Wang, J. Weiner

We report a measurement of the rate constant for associative ionization (AI) between excited Na(3p) atoms colliding within a single beam at a velocity of 11.9 ${\mathrm{msec}}^{\mathrm{\ensuremath{-}}1}$, corresponding to a temperature of 65 mK. The collisions take place in a narrow velocity class of excited atoms produced by crossing the collimated Na beam with a monomode dye laser at an angle of 45\ifmmode^\circ\else\textdegree\fi{}. Light polarized linearly in the collision plane yields an AI rate constant greater than that for circular polarization by a factor of 2. We find ${K}_{65\mathrm{m}\mathrm{K}{}^{\mathrm{lin}}}$ =(12.2\ifmmode\pm\else\textpm\fi{}4.3)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{3}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ and ${K}_{65\mathrm{m}\mathrm{K}{}^{\mathrm{cir}}}$ =(6.1\ifmmode\pm\else\textpm\fi{}1.8)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{3}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$. The experimental arrangement also permits absolute calibration of earlier crossed-beam measurements of the excitation function (cross section versus velocity) at conventional thermal beam kinetic energies. Present results together with earlier work show that the cross-sectional temperature dependence is in qualitative accord with theory.We report a measurement of the rate constant for associative ionization (AI) between excited Na(3p) atoms colliding within a single beam at a velocity of 11.9 ${\mathrm{msec}}^{\mathrm{\ensuremath{-}}1}$, corresponding to a temperature of 65 mK. The collisions take place in a narrow velocity class of excited atoms produced by crossing the collimated Na beam with a monomode dye laser at an angle of 45\ifmmode^\circ\else\textdegree\fi{}. Light polarized linearly in the collision plane yields an AI rate constant greater than that for circular polarization by a factor of 2. We find ${K}_{65\mathrm{m}\mathrm{K}{}^{\mathrm{lin}}}$ =(12.2\ifmmode\pm\else\textpm\fi{}4.3)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{3}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ and ${K}_{65\mathrm{m}\mathrm{K}{}^{\mathrm{cir}}}$ =(6.1\ifmmode\pm\else\textpm\fi{}1.8)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{3}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$. The experimental arrangement also permits absolute calibration of earlier crossed-beam measurements of the excitation function (cross section versus velocity) at conventional thermal beam kinetic energies. Present results together with earlier work show that the cross-sectional temperature dependence is in qualitative accord with theory.

Physical Review AMar 1, 199025 citations

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.

The photoionization cross sections of two even-parity excited states

5d6d\phantom{\rule{0.3em}{0ex}}^{3}D_{1}

and

6s7d\phantom{\rule{0.3em}{0ex}}^{3}D_{2}

of atomic Ba at the ionization-laser wavelength of

556.6\phantom{\rule{0.3em}{0ex}}\mathrm{nm}

were measured. We found that the total cross section depends on the relative polarization of the atoms and the ionization-laser light. With density-matrix algebra, we show that, in general, there are at most three parameters in the photoionization cross section. Some of these parameters are determined in this work. We also present the measurement of the radiative lifetime of five even-parity excited states of barium.

{K}_{65\mathrm{m}\mathrm{K}{}^{\mathrm{lin}}}

=(12.2\ifmmode\pm\else\textpm\fi{}4.3)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$

{\mathrm{cm}}^{3}

${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ and

{K}_{65\mathrm{m}\mathrm{K}{}^{\mathrm{cir}}}

=(6.1\ifmmode\pm\else\textpm\fi{}1.8)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$

{\mathrm{cm}}^{3}

${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$. The experimental arrangement also permits absolute calibration of earlier crossed-beam measurements of the excitation function (cross section versus velocity) at conventional thermal beam kinetic energies. Present results together with earlier work show that the cross-sectional temperature dependence is in qualitative accord with theory.