High-resolution infrared spectrum of the ν3 band in Ar–HCO+

Spectroscopic properties of Ar–HCO+ have been studied by exciting the C–O stretch of the HCO+ chromophore. The ionic complex is generated in a slit jet expansion with subsequent electron impact ionization. The spectra are obtained by direct absorption spectroscopy using a tuneable diode laser and production modulation. The ν3 band of the Ar–HCO+ is rotationally resolved and has a form consistent with a linear proton-bound complex. The band origin is at 2135.7073(4) cm−1 which is 48.24 cm−1 red-shifted compared to the value in free HCO+.