Diode Laser Spectrum of the Fundamental v2 Band of HNCO

Infrared spectrum of HNCO near 5 μm was measured by a diode laser spectrometer with source frequency modulation and Stark modulation methods. The subbands of the v2 fundamental band were identified for Ka = 0 to 4. The subband origins and the effective rotational constants for these subbands were determined. The rotational fine structure of the v2 band suggests that the levels are perturbed by accidental resonances.