Knowledge Bank

Recently the New Brunswick group {\textbf{87}} 557, 2009.} reported on the field-free detection and analysis of the $A3$$\Phi 4-X3\Phi 4$ band system of IrF. Here we report on the analysis Q(4)(15922 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$) branch feature of the (1,0) band of the $\mathrm{<mrow\; data-mjx-texclass="ORD">191</mrow>}$IrF isotopologue of that system recorded at field strengths of up to 3000 V/cm. The spectra are surprisingly complex at the achieved resolution of 40 MHz due to the presence of both the $\mathrm{<mrow\; data-mjx-texclass="ORD">191</mrow>}$Ir(I=3/2) and $\mathrm{<mrow\; data-mjx-texclass="ORD">19</mrow>}$F(I=1/2) magnetic hyperfine splitting. The determined permanent electric dipole moment, $\mu el$, for the $X3\Phi 4$ state is compared with that recently determined {\textbf{131}} 114315, 2009.} for the $X3\Phi 4$ state of isovalent CoF. The trend in $\mu el$ amongst the ground states of IrF, IrC and IrN {\textbf{104}} 8183, 1996.}will be discussed. Finally, a simple molecular orbital correlation diagram will be used to rationalize the change in $\mu el$ upon excitation from the $X3\Phi 4$ to $A3\Phi 4$ state.