CROSS SECTIONS FOR FORMATION OF EXCITED STATES IN A NITROGEN TARGET BY IMPACT OF 0.15- TO 1.0-MEV PROTONS

Protons in the energy range 0.15-1.0 MeV were incident on a molecular nitrogen target and the resulting emission was analyzed spectroscopically. Absolute measurements were made of the intensity of certain spectral lines. Cross sections are presented for the emission of two prominent lines of singly ionized atoms and for nine lines from the N2+ first positive band system. Cross sections for the population of the v′=0 and v′=1 vibrational levels of the B2 excited state of N2+ are obtained from the emission functions. In the present work, the proportion of N2+ ions formed in the excited state remains almost independent of impact energy, indicating that the excited N2+ ions are produced by simultaneous ionization and excitation of the target. The measured relative populations of two vibrational levels in the N2+ ion are shown to be in good agreement with the ratios of the relevant overlap integrals. An investigation of the emission of the N2 second positive system shows that it is mainly excited by secondary-electron impact, the cross section for proton impact excitation of the CΠ3 state of the N2 molecule being some three orders of magnitude less than that for electrons at the same impact velocity. This indicates the importance of spin conservation in governing the transitions which occur in collisional excitations by heavy-particle impact. © 1968 The American Physical Society.