HIGH-K (PROPELLER) STATES IN THE INFRARED-SPECTRUM OF THE AR-CO COMPLEX

The infrared spectrum of the weakly bound complex Ar-CO has been studi ed in the 4 . 7 mu m region of the CO stretching vibration by means of three complementary techniques: a continuous slit-jet supersonic expa nsion with a tunable diode laser, a long-path cooled cell with a tunab le diode laser, and a long-path cooled cell with a Fourier transform i nfrared spectrometer. Previous studies have characterized states of Ar -CO with K-a values up to 3 in the ground bending state, and up to 1 i n the first excited bending state. Here these studies are extended up to K-a = 6 by analysing subbands with K-a = 4 <-- 3, 3 <-- 4, 5 <-- 4, and 6 <-- 5, and thereby obtaining subband origins, rotational parame ters, and centrifugal distortion parameters which characterize these s tates. The results illustrate the relative stability and regularity of high-K (propeller) states, even if on close examination they are subj ect to perturbations, as compared with excited bending (windmill) and van der Waals stretching states in weakly bound T-shaped complexes.