ROTATIONAL SPECTRUM AND STRUCTURE OF THE AR3-HCL SYMMETRICAL TOP

Abstract

The Ar3–HCl tetramer has been identified via the observation of its microwave rotational spectrum using the pulsed nozzle Fourier transform technique. The rotational spectroscopic constants of the ground vibrational state have been obtained for the 35Cl/37Cl isotopes from measurements of the J=1→2 to J=4→5 transitions and their hyperfine structure. For Ar3–H35Cl, the values found for B0, DJ, DJK, and χaa are 843.8974(1) MHz, 2.333(2) and 1.818(6) kHz, and 31.006(5) MHz, respectively, and for Ar3–H37Cl, 825.9811(2) MHz, 2.211(5) and 1.940(12) kHz, and 24.481(8) MHz. The cluster is a symmetric top with the HCl along the C3 axis, its H end directed towards the Ar3 trimer. In its torsional oscillations, the HCl makes an average angle of 36.91° with the symmetry axis. The chlorine isotopic substitution leads to values of 3.8510 and 4.0024 Å for the Ar–Ar and Ar–Cl distances. The results of the present study are compared with those reported earlier for the Arm–HF (m=1,2,3) and Arm–HCl (m=1,2) clusters.