Dipole Moment and Hyperfine Parameters of H35Cl and D35Cl

The molecular-beam electric resonance spectra of H 35Cl and D 35Cl have been analyzed. The molecular constants obtained in the observed states are as follows (numbers in parentheses are the errors in the final significant figures): HCl35υ = 0, J = 1υ = 0, J = 2υ = 1, J = 1υ = 2, J = 1eqQCl(kHz)− 67 618.93(47)− 67 638.53(15)− 69 272.89(93)− 70 908.1(24)CH(kHz)− 41.80(25)− 41.68(4)− 41.09(24)− 39.94(94)CCl(kHz)+ 53.851(42)+ 53.887(14)+ 58.597(45)+ 63.68(17)μ(D)1.1085(5)1.1085(5)1.1390(10)1.1685(10)DCl35υ = 0, J = 1υ = 0, J = 2υ = 0, J = 3υ = 1, J = 1eqQD(kHz)+ 187.36(30)+ 187.0(28)+ 184.8(38)eqQCl(kHz)− 67 393.38(9)− 67 403.32(29)− 67 418.00(10)− 68 583.1(10)CD(kHz)− 3.295(46)− 3.308(80)CCl(kHz)+ 27.426(7)+ 27.430(28)+ 29.121(62)μ(D)1.1033(5)1.1033(5)1.1256(10) The above dipole moments were used in conjunction with available absolute infrared intensity measurements of vibrational bands to obtain the dipole moment function of the molecule. The derivatives with respect to the internuclear distance R, evaluated at Re, for H 35Cl are: (dμ / dR)e = + 0.925 ± 0.020 D/Å; (d2μ / dR2)e = + 0.16 ± 0.11 D/Å2; (d3μ / dR3)e = − 3.83 ± 0.90 D/Å3; (d4μ / dR4)e = − 9.3 ± 4.5 D/Å4. In addition, an isotope effect in the dipole moment due to a violation of the Born–Oppenheimer approximation was observed by comparing the relative HCl and DCl dipole moments. The distance derivatives of the field gradient, qCl, at the 35Cl nucleus were also determined: (dqCl / dR)e = (+ 13.52 ± 0.55) × 1015 (esu/cm3)/Å; (d2qCl / dR2)e = (− 23.9 ± 3.3) × 1015 (esu/cm3)/Å2. The rotational magnetic moment of H 35Cl (υ = 0, J = 1) was measured, yielding the molecular g value: gJ = + 0.47 ± 0.03. This parameter, when combined with other available data, allowed a better determination of relative values of Re in H 35Cl and D 35Cl: Re(HCl35) = 1.274700 ± 0.000010 Å; Re(DCl35) = 1.274652 ± 0.000005 Å. The isotope effect on Re is apparent in this determination.