Because of the confusion between two low odd levels 1218 cm-1 apart, the complete system of levels of Nd II built on the core f3 had to be revised with the help of the 144Nd-150Nd isotope shift. The lowest odd level f3d2 6M13/2 is now at 8009.810 cm-1, 96 levels have been shifted and 126 new levels have been found. The new identifications rely upon parametric studies of the sub-configurations 4f35d6s + 4f3(4I)5d2 + 4f4(5I)6p (115 interpreted levels) and 4f3(4I)5d6p + 4f3(4I)6s6p (124 interpreted levels).

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Penning ionization (PI) occurring during the collision of a Rydberg atom Rb(nl) with a resonant state K(4P) or Rb(5P) is analyzed theoretically. By using a semiclassical approach, we calculate the rate coefficients corresponding to both the direct and exchange decay channels. We implement the method by deriving various approximations for the exchange and direct decay widths. The radiative mechanism is found to dominate the thermal-energy quenching of alkali atoms by PI, the exchange being negligible. The calculated values are in reasonable agreement with the available experimental results.