Knowledge Bank

A modified form of the equation derived by Strickler and Berg for calculating radiative lifetimes is presented which is applicable to symmetry forbidden transitions. Using this equation radiative lifetimes of various vibronic levels of the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A2$ state of formaldehyde and the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}B2u$ state of benzene are calculated. The lifetimes calculated for the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A2$ state of formaldehyde are in good agreement with experimental values of Lee and Miller. The lifetimes calculated for the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}B2u$ state of benzene are two to three times longer than the experimental values of several investigators Possible sources of the discrepancies found in the benzene values are discussed.