Europhysics Letters (EPL)

Ionizing Collisions Between Two Laser-Excited Atoms: Separation of Penning and Photoionization by High-Resolution Electron Spectrometry

H Dengel, M.‐W. Ruf, Hartmut Hotop

Published Sep 10, 1993• 6 citations

Abstract

Using transverse laser excitation of a single collimated atomic sodium beam in combination with an efficient electron spectrometer, we have studied collisional (= Penning) and photoionization processes involving the laser-excited Na(3 p 3/2 ) and Na(3 d 5/2 ) atoms. As a result of our high electron energy resolution (6 meV) we have for the first time been able to measure the polarization-dependent lineshapes of the Penning electron spectra for collisions between two laser-excited atoms and to reliably separate overlapping contributions due to Penning and photoionization.

DOI: 10.1209/0295-5075/23/8/005

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Europhysics Letters (EPL)

Ionizing Collisions Between Two Laser-Excited Atoms: Separation of Penning and Photoionization by High-Resolution Electron Spectrometry

H Dengel, M.‐W. Ruf, Hartmut Hotop

Published Sep 10, 1993• 6 citations

Publisher

Abstract

DOI: 10.1209/0295-5075/23/8/005

Related papers

Efficient collisional dissociation of Na{sub 2}{sup +} by laser-excited Na (3p)

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Penning ionization of alkali metal atoms by barium atoms in Rydberg states

Charles E. Burkhardt, M. Ciocca, W. P. Garver +4 more

Quantum Electronics and Laser Science ConferenceApr 24, 19890 citations

The ionization of

6sns^{1}S_{0}

Rydberg states of

^{138}\mathrm{Ba}

has been investigated by high-resolution electron spectroscopy. The Rydberg states were excited by two cw dye lasers via the

6s6p^{1}P_{1}

level. The electron spectra show rich structure between 0.025 and 3 eV, largely attributable to collisional (Penning) ionization, photoionization, and autoionizing transitions. The first process might be interpreted as superelastic scattering of the Rydberg electron by optically pumped

\mathrm{Ba}(6s6p^{1}P_{1})

\mathrm{Ba}(6s5d^{1}D_{2})

atoms.

We report cross-section measurements of the associative-ionization process, Na(3

{\mathit{p}}^{2}

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

)+Na(3

{\mathit{p}}^{2}

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

)\ensuremath{\rightarrow}

{\mathrm{Na}}_{2}^{+}

+e as a function of velocity, alignment, and orientation in the collision energy range from 300 to 5 K. Two independently tunable laser beams select narrow velocity classes of excited sodium in a well-collimated atomic beam. Circular and linear polarization of the excitation lasers permits alignment and orientation of the excited atoms in the two velocity classes. The excitation functions show pronounced differences reflecting different molecular pathways to the final product, and they bridge the energy range between conventional and ``cold'' collision dynamics.

{\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.