Infrared diode laser spectroscopy of the ν 19a band of aniline in a supersonic jet

The diode laser absorption spectrum of the ν 19a band of aniline cooled in a supersonic expansion has been recorded and transitions with low J , K a and K c values (2–28) are reported. The band center has been found at ν 0 =1504.297 cm −1 and rotational constants for the upper state have been determined from a least-squares fitting to the experimental data. The effect of the centrifugal distortion has also been studied, and approximate values of quartic constants are provided. In addition, the possible effect of the inversion mode of the NH 2 group on the ν 19a mode is analyzed.