MOLECULAR ROTATIONAL ZEEMAN EFFECT IN THIOFORMALDEHYDE

Abstract

The high-field rotational Zeeman effect has been observed in thioformaldehyde. The magnetic susceptibility anisotropies are $2X_{aa} -X_{bb} - X_{cc} = 52.3 \pm 1.1 ( x \ 10^{-6} erg/G^{2}$. mole) and $2X_{bb} - X_{aa} - X_{cc} = - 5.1 \pm 0.7$. The molecular g values with uniquely determined signs are $g_{aa} = - 5.2602 \pm 0.0068$, $g_{bb}= - 0.1337 + 0.0004$, and $g_{cc} = - 0.0239 \pm 0.0004$. c is the out-of-plane axis and the $a$ axis is the dipole axis. $g_{aa}$ represents the largest molecular g value yet measured. Use of these five Zeeman parameters and the known structure gives the molecular quadrupole moments: $Q_{aa} = 3.0 \pm 0.7 (x \ 10^{-26} esu.cm^{2}), Q_{bb} = - 2.4 + 0.5, Q_{cc} = - 0.6 \pm = 1.1$; the diagonal elements of the paramagnetic susceptibility tensor: $X_{aa}^{P} = 45.8 \pm 0.3 (x \ 10^{-6} erg/G^{2}$.mole), $X_{bb}^{p} = 88.3 \pm 0.6, X_{cc}^{p} = 82.6 \pm 0.6$; and the anisotropies in the second moments of the electronic charge distribution. By estimating the out-of-plane second moment of the electronic charge distribution as $< c^{2} > = 4.6 \pm 0.4 (x \ 10^{-16} cm^{2})$ using free atom values, we have evaluated the remaining, individual second moments of the electronic charge distribution to be $\langle a^{2}\rangle = 21.1 \pm 0.6 (x \ 10^{-16} cm^{2})$ and $\langle b^ 2\rangle = 6.6 \pm 0.5$. The diagonal elements of the diamagnetic and total magnetic susceptibility tensor also follow from the above estimation of $\langle c^{2}\rangle $ and are $X_{aa}^{d} = - 47.5 \pm 2.5(x 10^{-6} erg/G^{2}.mole), X_{bb} ^{d}= - 109.1 \pm 3.0, X_{cc}^{d} = - 117.6 \pm 3.4, X_{aa} = -1.7 \pm 2.5, X_{bb} = - 20.8 \pm 3.1$, and $X_{cc} = - 35.0 \pm 3.5$, giving the bulk magnetic susceptibility as $X = \frac{1}{3} (X_{aa} + X_{bb} + X_{cc}) = - 19.2 \pm 1.8 (x \ 10^{-6}\ erg\ /G^{2}.mole)$. These values are then compared to those of the oxygen analog, formaldehyde, and trends in this pair are compared to several other previously studied oxygensulfur analogs.