Weak bands in the far-infrared spectrum of HCNO

Several weak transitions in the far-infrared spectrum of H ¹²C ¹⁴N ¹⁶O between the (0000 _v) levels with v = 2, 3, and 4 have been analyzed. Vibrational levels of improved accuracy have been calculated for both the (0000 _v) series ( v ≦ 5) and the (0001 _v) series ( v ≦ 3). For the latter, some inconsistencies in previous assignments have been removed. Two transitions from the (00020) ² level have been assigned tentatively. The two lowest bands of the (0000 _v) series of H ¹³C ¹⁴N ¹⁶O have been found. Two new types of graphical plots have been used in the assignment.