Probing Hypervalent Radicals by Neutralization−Laser Photoionization Mass Spectrometry

The metastability of hypervalent dimethyldeuteroxonium radicals ( 1a • ), generated by fast collisional electron transfer from organic targets in the gas phase, is probed by laser photoionization at 488 and 514.5 nm. A fraction of 1a • is photoionized at these wavelengths, indicating formation of metastable 1a • with vertical ionization energies of <2.5 eV. Ab initio calculations find a bound 2 A‘‘ state for dimethylhydroxonium 1b •, which is characterized as a 3p Rydberg state of 2.22 eV vertical ionization energy. No potential energy minimum is found for the 2 A‘ ground electronic state of 1a,b •, which is predicted to dissociate exothermically by O−H bond cleavage.