Determination of the structure of ArHCl

Abstract

The radio frequency and microwave spectra of K = 0 states of ArHCl and ArDCl have been measured by molecular beam electric resonance spectroscopy. The rotational and hyperfine structure constants for the lowest vibrational state of the four isotopic species are ArH35 ClArD35 ClB̄ = (B+C)/2 = 1.678511 (5)GHzB̄ − 2DJ = 1.657596 (10)GHzDJ=20.33 (20)kHz(eqQ)aC1 = −36.250 (20)MHz(eqQ)a=−23.027(10)MHz(eqQ)aD = +102.3 (50)kHzμa=0.81144(10)Dμa=1.00355(70)DArH37 ClArD37 ClB̄ − 2DJ = 1.631566 (5)GHzB̄ − 2DJ = 1.611876 (10)GHzOnly the lowest vibrational state has been observed. The molecule is extremely nonrigid. The average Ar–Cl distance is 4.006 Å in ArHCl and 4.025 Å in ArDCl. The Ar–Cl–H angle is acute and the amplitude of the zero point angle bending is extremely large. The average Ar–Cl–H angle is near 45°, while the average Ar–Cl–D angle is near 34°. The vibrational frequency of Ar–HCl bond stretching is computed to be 32.2 cm−1 from the observed centrifugal distortion constant.