Molecular beam photoionization study of CO, N2, and NO dimers and clusters

Abstract

Photoionization efficiency (PIE) data for (CO)⁺₂, (N₂)⁺₂, and (NO)⁺₂ have been obtained near the thresholds using the molecular beam method. The ionization energies (IE) for (CO)₂, (N₂)₂, and (NO)₂ were measured to be 13.05±0.04 eV (950±3 Å), 14.69±0.05 eV (844±3 Å), and 8.736±0.002 eV (1419.2±0.3 Å), respectively. Using these values, the known IE’s for CO, N₂, and NO, and the estimated binding energies for (CO)₂, (N₂)₂, and (NO)₂, the bond dissocations energies for CO⁺⋅CO, N⁺₂⋅N₂, and NO⁺⋅NO were deduced to be 0.97±0.04, 0.90±0.05, and 0.598±0.006 eV, respectively. From the analysis of the PIE curve for (NO)⁺₂, the IE’s of (NO)₂ to NO⁺(?¹S⁺, v = 1)⋅NO and NO⁺(?¹S⁺,v = 2)⋅NO were determined to be 8.997±0.007 eV (1 378±1 A°) and 9.253±0.013 eV (1 340±2 A°), respectively. This measurement supports the conclusion that the bonding of NO⁺ in NO⁺⋅NO is stronger than that of NO, but weaker than that of NO⁺. The IE’s for (CO)₃, (N₂)₃, and (NO)_{n = 3–6} were also measured.