Improved ground state rotational constants for the argon–hydrogen fluoride dimer

Ten new rotational transitions, J(4<--3) to J(13<--12), of the argon–hydrogen fluoride dimer (Ar–HF) have been measured in the ground vibrational state. The spectra were obtained in the microwave spectral region from a slit supersonic expansion. In a combination fit with previous microwave measurements [A. Dixon, C. H. Joyner, F. A. Baiocchi, and W. Klemperer, J. Chem. Phys. 74, 6539 (1981)] and high-J infrared spectra of the HF stretch (1000)<--(0000) [G. T. Fraser and A. S. Pine, J. Chem. Phys. 85, 4890 (1986)], the values for the ground rotational constants have been improved considerably. The improved values for the constants allow predictions of ground state energies within 1 MHz up to J=20 and within 30 MHz for J values up to 40.