ROTATIONAL SPECTRA AND MOLECULAR-STRUCTURES OF ARHBR AND KRHBR

Rotational spectra have been observed for four isotopes of ArHBr and ArDBr and eight isotopes of KrHBr and KrDBr using a Fabry-Perot Fourier transform spectrometer with a pulsed supersonic nozzle as the molecular source. The rotational constants in the ground vibrational state, B̄0, with their centrifugal distortions, DJ, as well as Br nuclear quadrupole coupling constants, χa, are given. In addition, an important centrifugal distortion of the Br quadrupole coupling constant, D χ, an indicator of the coupling between the radial and angular potentials, is given for ArHBr and KrHBr. The Br spin-rotation interaction, c, in ArHBr is also obtained. The results are: Isotope B̄0(MHz) DJ(kHz) χa(MHz) Dχ(kHz) c(kHz) ArH 79Br 1106.66951(17) 12.397(4) 173.199(6) 18.42(26) 1.09(13) ArH 81Br 1097.58109(15) 12.226(3) 144.793(5) 15.21(23) 0.67(12) ArD 79Br 1087.50889(27) 8.497(6) 276.223(9) 14.73(41) 0.94(20) ArD 81Br 1078.59315(22) 8.352(5) 230.878(8) 12.26(37) 1.02(16) 82KrH79Br 692.31400(14) 2.6579(14) 228.18(9) (7.57) a 84KrH79Br 684.22952(15) 2.5973(11) 228.26(14) 7.57(29) 86KrH79Br 676.51549(36) 2.5364(30) 228.41(36) (7.57)a 82KrH81Br 683.71030(41) 2.6003(40) 191.26(30) (5.88)a 84KrH81Br 675.62442(14) 2.5266(11) 190.78(14) 5.88(28) 86KrH81Br 667.91018(13) 2.4634(10) 190.78(14) (5.88)a 84KrD79Br 675.84862(14) 2.1900(10) 318.18(14) 5.05(30) 84KrD81Br 667.40217(20) 2.1384(15) 265.85(19) 4.76(40) aValues of D χ in parentheses were fixed in the least squares fit. The molecular structures are consistent with a linear equilibrium geometry with the H(D) atom located between Br and the rare gas atoms. The complexes undergo large amplitude vibrations and estimates of the bending and stretching force constants and frequencies are given. By combining the bending, stretching, and their coupling, we have obtained the harmonic bending and stretching force constants (ks1 and kb1) and 6/12 Lennard-Jones potential parameters (ε and Re) for ArHCl, KrHCl, ArHBr, KrHBr. The results are ks1(mdyn Å-1) k b1(mdyn·Å) ε(cm-1) Re(Å ) ArHCl 0.0164 0.00151 183.5 4.0061 KrHCl 0.0203 0.00219 240.3 4.1525 ArHBr 0.0166 0.00142 206.0 4.2113 KrHBr 0.0192 0.00211 247.3 4.2969. © 1980 American Institute of Physics.