Direct determination of the adiabatic ionization energy of NO2 as measured by guided ion-beam mass spectrometry

The adiabatic ionization energy (IE) of NO2 is measured to be 9.60±0.03 eV by studying the charge-transfer reactions of Zn+, NO+, and CH3I+ with NO2 and those of NO+2 with α,α,α-trifluorotoluene and CH3I using guided ion-beam mass spectrometry. This value confirms the accuracy of a very precise spectroscopic value measured by Haber et al. [J. Chem. Phys. 144, 58 (1988)] and Tanaka and Jursa [J. Chem. Phys. 36, 2493 (1962)], IE(NO2)=9.586±0.002 eV, but is much lower than many other measurements that are limited by very unfavorable Franck–Condon factors. The mechanism that allows the charge-transfer reactions to occur at the thermodynamic limit is discussed by examining qualitative potential-energy surfaces for the charge-transfer processes.