Knowledge Bank

The $\mathrm{<mrow\; data-mjx-texclass="ORD">83</mrow>}Kr$ nuclear quadrupole coupling constants were measured for the $Kr-PF3$ complex using a FTMW spectrometer. These values were compared with those expected from the Sternheimer equation $qi=qi(1---\gamma \infty )$ for four possible structures which are consistent with the rotational constants. The value of $qi\circ$ (field gradient arising from $PF3$) for each structure was calculated using GAUSSIAN86 for free $PF3$. Information on $\gamma \infty$ (Sternheimer shielding factor) necessary for the analysis was obtained by comparison with other $\mathrm{<mrow\; data-mjx-texclass="ORD">83</mrow>}Kr$ complexes in the literature. The conclusion was that only one structure is consistent with the quadrupole coupling constants viz the conformation placing the Kr over a $PF2$ face. A comparison between ab initio calculations and a multipole expansion approximation to estimate the electric field gradient at the rare gas site in van der Waals complexes will be presented.