Magnetic Susceptibility Anisotropy, Molecular Quadrupole Moment, and the Sign of the Electric Dipole Moment in OCS

Abstract

The molecular Zeeman effects of ¹⁶O¹²C³²S and ¹⁶O¹²C³⁴S have been observed under high resolution in magnetic fields up to 30 000 G. Conventional microwave spectroscopy is combined with a 6‐ft long magnet to yield accurate first‐ and second‐order magnetic field parameters. The magnetic susceptibility anisotropy of the OCS molecule is ${\text{χ⊥–χ∥\hspace{0.17em}=\hspace{0.17em}(9.27\hspace{0.17em}±\hspace{0.17em}0.10)\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−6}}\mathrm{erg}/{\mathrm{G}}^2·\mathrm{mole}$ . The molecular $g$ values for the two isotopes obtained from the $\text{J\hspace{0.17em}=\hspace{0.17em}0\hspace{0.17em}→\hspace{0.17em}J\hspace{0.17em}=\hspace{0.17em}}$ transitions are ${\mathrm{g\perp (}}^{16}{\mathrm{O}}^{12}{\mathrm{C}}^{32}\mathrm{S}\text{)\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}0.028711\hspace{0.17em}±\hspace{0.17em}0.00004}$ and ${\mathrm{g\perp (}}^{16}{O}^{12}{C}^{34}\text{S)\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}0.028127\hspace{0.17em}±\hspace{0.17em}0.00004}$ . These data yield the sign of the molecular electric dipole moment which has ⁻OCS⁺ polarity. Combining $\mathrm{\chi \perp –\chi \parallel }$ and ${\mathrm{g\perp (}}^{16}{O}^{12}{C}^{32}\mathrm{S)}$ gives the molecular quadrupole moment of $Q_{\parallel }{(}^{16}{O}^{12}{C}^{32}{\text{S)\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}(0.88\hspace{0.17em}±\hspace{0.17em}0.15)\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−26}}\mathrm{esu}·{\mathrm{cm}}^2$ .