Near infrared emission spectrum of HCN

To record the infrared emission of hot molecular gases an optimized emission apparatus for the Bruker IFS 120 HR high-resolution FT-IR spectrometer has been constructed. Using this apparatus the hot gas emission spectrum of HCN at 1420 K has been recorded in the wavenumber region of 6000-6800 cm−1 with a resolution of 0.044 cm−1. This work reports the analysis of 33 bands with 58 subbands (9200 line positions). Thirty-seven rovibronic states of HCN including v1v2lv3=2880 at 12 603 cm−1 have been characterized for the first time and for 25 other states it was possible to improve the existing spectroscopic constants substantially. The very dense emission spectrum with many overlapping features was analyzed with new spectrum analysis software implemented using the MathematicaTM computer algebra system. Spectroscopic constants have now been determined for 220 HCN rovibronic states. For 102 states the rovibrational spectroscopic constants have been determined for the first time or improved substantially using emission spectra measured in Giessen.