Generation of an H 3+( v = 0) beam and its diagnosis from the observation of its polar dissociation in collision with He

Abstract

Ground state H 3 + ions in their lowest vibrational level were produced, and the initial vibrational state of the H 3 + ions was qualitatively observed as a function of the source pressure. Quantitatively, the polar dissociation channel was studied in order to verify the initial vibrational state of the ions. The energy distributions of H + and H −, generated from the collisional dissociation of H 3 + in He at 9 keV of projectile energy, resulting from the polar dissociating channel, were measured in coincidence. The good agreement between the center of mass energy threshold of the proton distributions from the polar dissociation process and the theoretical potential curves for the adiabatic Born-Oppenheimer energies of the H 3 + ions confirms the vibrational cooling of the H 3 + beam by operating the ion source at high pressure. We conclude that the process is effectively originated from H 3 +( v=0).