Neutral sodium-water clusters are formed in a "pickup" source, injection of a beam of Na atoms into the expansion zone of a pulsed nozzle-jet beam of water vapor seeded into an argon carrier gas. They are detected by near-uv one-photon ionization with a pulsed laser and time-of-flight mass spectroscopy. NaCHaO^-cluster-ion signals up to n = l2 are seen, « = 4 showing a very pronounced abundance. The ionization potential of NaOHa is determined to be 4.379 ±0.002 eV.

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Electronic to vibration-rotational-translational energy transfer in the quenching of Na(3 2P3/2) by CO has been studied with state of the art crossed atomic, molecular, and laser beam techniques at 0.16 eV initial kinetic energy, and by ab initio CI calculations for the potential energy surfaces involved in the process. Double differential quenching cross sections are measured as a function of scattering angle and energy transferred to the molecule. A pronounced structure in the energy transfer spectra as well as a partial backward scattering is attributed to two different mechanisms, a ’’direct’’ one and one which proceeds through ’’complex’’ formation. The observations are explained by the calculated potential energy surfaces (PES) for the first excited states Ã 2A′(Ã′ 2A″) and the ground state X̃ 2A′ which exhibit two crossing seams below the 2.1 eV excitation energy: (i) one for colinear approach of Na* on the carbon side of CO with its lowest energy 1.06 eV at Rc(Na–CO)= 5.5a0, rc(C–O) = 2.35a0 responsible for the direct process and (ii) one for colinear approach of Na* on the oxygen end of CO with 1.28 eV at Rc= 4.9a0 and rc= 2.47a0, allowing the quenching after ’’complex’’ formation. The angularly integrated cross sections are maximal (27 Å2/eV) at an energy transferred to the molecule equivalent to five vibrational quanta. Comparison with bulk data suggests strong rotational excitation (two vibrational quanta in the average) as can be rationalized from the anisotropy of the X̃ 2A′ PES near the crossing region. Total quenching cross sections and their temperature dependence can be explained by the absorbing sphere model using the calculated location and energy of the crossing seams.

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The quenching of excited Na* (4d,5s,4p,4s) by N2 has been studied in a crossed atomic and molecular beam apparatus at thermal collision energies. The sodium atoms are excited by two laser beams of different wavelengths to either the 42D5/2 or 52S1/2 state, via the intermediate 32P3/2 state. For both excitation schemes optical relaxation processes lead to a population in the 42P3/2 and 42S1/2 states of several percent. The relative densities of the excited states have been calculated from rate equations using stationary conditions. The measured energy transfer spectra show high scattering intensities at low kinetic energies together with some structure at medium energies. This structure can be partially disentangled using the results of the previously studied Na*(32P3/2)+N2 quenching process. The main conclusion is that collisional deexcitation to the Na(3s) ground state is negligible, whereas among the higher levels the collisional energy transfer cross sections are between 0.5 and 7.5 times the magnitude of the 3p–3s quenching cross section and they are strongly forward peaked in the same way. Relative values for the differential quenching cross sections are reported.