Knowledge Bank

The vibronic intensity arising from Herzberg-Teller effect for $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A\prime \prime (n\Pi \ast )$ state of benzaldehyde are studied by the calculations of configuration interaction with INDO wave function. The discrepancy between calculations and experiment is quite serious, especially for aldehyde H-wag vibration mode. However, the same method gives a reasonable account of phosphorescence vibronic intensity for $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}A\prime (n\Pi \ast$) which is supposed to have very similar intensity borrowing mechanism as $A|prime\prime (n\Pi \ast$) state. Several possible candidates to explain this interesting enigma are proposed.