Observation of the infrared nu 2 band (CH stretch) of protonated hydrogen cyanide HCNH +

Crofton and Oka (1983) have conducted a study on the infrared spectrum of the nu-3 band of NH4(+), and have called for theoretical predictions of the vibrational frequencies of other ions, taking into account protonated hydrogen cyanide H2CN(+), protonated methane, and protonated acetylene. In response to this call, three theorists have provided predictions of the vibrational frequencies of the HCNH(+) ion. The present investigation is concerned with the first successful observation of the infrared vibration-rotation spectrum of the fundamental nu-2 band (CH stretch) of this molecular ion. The values of the constants obtained experimentally are in excellent agreement with the theoretically obtained data. This agreement shows the quality and value of the ab initio calculations which are now possible.