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

Photochemistry of an N(2) 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 ((2)D) and N ((2)P) atoms, N(2) (A) molecule and linear-N(3) (l-N(3)) radical after excitation of icy N(2) at 121.6 nm. Irradiation at 190 nm is shown to be an effective way to eliminate the l-N(3) radical. After the photolysis and photoelimination of the l-N(3), we initiate synthesis of l-N(3) via the thermal ramping of the sample in temperature range 3.5 to 20 K. In addition, the emission from the N ((2)D) atom was observed during the thermal ramping process. These behaviors indicate that a long-lived N ((2)D(long)) atom is generated in the VUV-photolyzed N(2) ice. A comparison of the variations of the visible emission of N ((2)D) and the infrared absorption of l-N(3) with time indicates that the long-lived N ((2)D(long)) dominated the thermal synthesis of l-N(3). The results have enhanced suggestion and understanding of the conversion for nitrogen species in cold astrophysical environments with VUV irradiation.