Knowledge Bank

The spectrum of $CH3AsF2$ was investigated over the range 10-33 kMc/sec. Three Q-branches $(K=5\to 4,6\to 5,7\to 6)$ and two R transitions $(J=2\to 3,K=2\to 3;J=3\to 4,K=3\to 4)$ were fitted by a Hamiltonian which included terms for overall rotation, internal rotation, nuclear quadrupole coupling, and centrifugal distortion. The reciprocal moments of inertia are $A=5414.49\pm 0.04$ Mc/sec, $B=5381.28\pm 0.03$ Mc/sec, and $C=3871.88\pm 0.03$ Mc/sec. The b-axis is perpendicular to the plane of symmetry. The height of the internal rotation barrier (assumed to be sinusoidal) is $466\pm 10$ $cm-1$. With the bond length $\lambda CH=1.095$ {\AA} assumed, the spectral date yield $\Lambda AsC=1.930\pm 0.010$, {\AA}, $\Lambda AsF=1.734\pm 0.005${\AA}, , , . The quadrupole coupling constants for $As75$ are $eQqee=-220\pm 4$ Mc/sec and $\eta o=(qbb-qaa)/q00=-1.20\pm 0.05$.