Dissociation Energy of N2

Thermal reaction and luminescence of long-lived N 2D in N2 ice

Photochemistry of an N₂ ice and thermal reaction of the irradiated sample were studied with vacuum-ultraviolet (VUV) light from a synchrotron. Concurrent detection of infrared absorption and visible emission spectra provide evidence for the generation of energetic products N (²D) and N (²P) atoms, N₂ (A) molecule and linear-N₃ (l-N₃) radical after excitation of icy N₂ at 121.6 nm. Irradiation at 190 nm is shown to be an effective way to eliminate the l-N₃ radical. After the photolysis and photoelimination of the l-N₃, we initiate synthesis of l-N₃ via the thermal ramping of the sample in temperature range 3.5 to 20 K. In addition, the emission from the N (²D) atom was observed during the thermal ramping process. These behaviors indicate that a long-lived N (²D_long) atom is generated in the VUV-photolyzed N₂ ice. A comparison of the variations of the visible emission of N (²D) and the infrared absorption of l-N₃ with time indicates that the long-lived N (²D_long) dominated the thermal synthesis of l-N₃ The results have enhanced suggestion and understanding of the conversion for nitrogen species in cold astrophysical environments with VUV irradiation.

The dissociation energy of the nitrogen molecule

The electron-induced dissociation of nitrogen by essentially monoenergetic electrons has been studied in a mass spectrometer. It has been found that there are three ways by which the atomic nitrogen ions are produced, namely, those in which the accompanying nitrogen atom is produced in its three states, 4 S 0 , 2 D 0 , and 2 P 0 ; the atomic nitrogen ion being always formed in its ground ( 3 P ) state. The appearance potentials at which these three processes occur lead unequivocally to the conclusion that the dissociation energy of the nitrogen molecule is 9·756 eV.