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Using resonant two-photon excitation of a metastable Ne(Zp'3s 'Pod beam by two singlemode cw dye lasers, we have measured reduced widths T,=n"T. for the four Ne(Zp'(2Pp,,,) nd' [Kl,) autoionidngresonance series (IKl,=[!l:, [$I2,[;l2, and If],). The resulting values are r.= l67(7), 350(7), 87(2), and 73(3) m?, respectively, in good agreement with predictions by a semiempirical multichannel quantum-defect analysis involving complex quantum defects.

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High resolution energy spectra of electrons and ions resulting from thermal energy collisions of hydrogen and deuterium atoms with state-selected metastable Ne(3s3P2, 3P0) atoms are reported. The electron spectra for Ne(3P2)+H(D) are very broad: The high energy part due to formation of Nell § (NeD +) bound states (associative ionization), amounts to about 30 % of the ionizing events, whereas the dominant part of the spectrum including a prominent low-energy peak is due to Penning ionization out of a strongly-attractive entrance potential curve. Comparison of the spectra with quantum mechanical fit calculations yields fairly accurate information on this potential, in particular its well depth De[Ne(3p2)-H,D]=2.0(1)eV. The spectra for Ne(3Po)+H,D are comparatively narrow with much lower cross sections than the one for the Ne(3P2) state. The corresponding entrance channel is a weakly bound van der Waals molecule with a well depth below 0.1eV. A perturbation calculation of the Ne(3s)+H(ls) potential energy curves at large distances explains the observed difference between the Ne(3P2)+ H(D) and Ne(3P0)+H(D) systems. Symmetry arguments are given that the major contribution to the Ne(3P2)+H(D) spectra is due to the 22; potential.

Using mass spectrometry and electron spectrometry, we have studied ionization of Ar and Kr atoms in thermal energy collisions with laser-excited short-lived Ne(2p5 3p J=1,2,3) atoms. The cross sections show a strong statedependence, which is reproduced in calculations based on theoretical potential energy curves and a single exponential autoionization width. Significant polarization effects have been observed in the total and partial ion yields and in the electron spectra; they can only be explained with R-dependent autoionization probabilities favouring o + o electron transfer.