Knowledge Bank

The two dipole allowed subbands of the $3\nu 3$ band of $SF6$ have been recorded at T=160 K with near Doppler-limited resolution using a tunable laser difference-frequency spectrometer. From a fit of over four hundred lines, we determined the anharmonic parameters $X33,C33$, and $T33$ to be in close agreement with previous estimates. These parameters lead to the interpretation of one strong subband with $(nx,ny,nz)=(3,0,0)$ character and one very weak subband with (2,1,0) character in a Cartesian vibrational basis. The remaining second order spectroscopic parameters are in excellent agreement with their $\nu 3$ values. The overall standard deviation of our fit is $\sigma =3.4\times 10-4$ $cm-1$. We also have the most accurate determination of the ground state $B0$ to date: [B_{0} = 0.091071 \pm 0.000005 cm^{-1}]