High-resolution translational energy spectroscopy is an effective means of obtaining detailed state-selective information, permitting systematic investigation of spin conservation in collisional processes. In this paper, we examine collisional excitation of one selected singlet (N3 and one non-singlet ( 0 3 target by a variety of projectile ions, providing a kaleidoscope of assorted effects.The concept of spin conservation in collisional processes first appeared in an article on quantum mechanics written by Eugene Wigner during his Goettingen period,' and has been the subject of numerous studies ever since. Early experimental support for spin conservation came from the work of Beutler and Eisenschimme12 who monitored the triplet and singlet radiations emitted by excited mercury atoms in a gaseous discharge. They found that addition of metastable krypton ('P) to the discharge enhanced the triplet radiation without substantially affecting the intensity of the singlet radiation. This can be understood in terms of the multiplicities of the participating atoms in the two processes:The first of these is in accord with the spin-conservation requirement and therefore leads to enhancement of the triplet radiation, whereas the second process violates spin conservation and is accordingly suppressed. Contemporary investigations by M~o r e~.~ for inelastic collisions of N+ ions with inert gas atoms and diatomic molecules (N, and 0,) revealed that spin conservation was generally observed for all excitation and deexcitation processes, except for some weak spin violation attributed to strong spin-orbit coupling in the relevant ion-atom/ion-molecule systems. However, one of their reported spin non-conserved processes, involving the simultaneous atomic N+('D+ IS) and molecular 0,(X3X;+ G 'Ag) transitions in N+-02, was not detected in our recent high-resolution studies of this collision ~y s t e m .~ In single electron capture, studies by Sat0 and Moore6 on capture by N2+ in He and Ne also confirmed spin conservation in all observed channels. This is in accord with our own recent investigation of single electron capture (SEC) by N2+ ions, as well as SEC by C2+, C3+ and 02+ from He, Ne and Ar By contrast, double electron capture (DEC) processes are often associated with spin violation. This is exemplified by the observation of Fourier et a[." in DEC collisions of H' with Xe atoms in translationalenergy studies. Our own studies involving double electron capture by Xe3+ and Kr3+ in Ar and KrI2 and Ar4+ states is strictly forbidden with the 2H+ and He2+ product target ions being permanent singlets. They found that the results for collisions of He2+ with H2 were in accord with the spin rule, but significant triplet emissions following He2+/He collisions indicated a spin violation and were attributed to the dominations of short range effects. Our current observations", l3 appear to support this view.The Wigner spin-conservation rule', 4, l9 requires that the total spin angular momentum should remain unchanged in the course of a collision...