Does light absorption result in a momentarily weaker bond?
it may happen but it is not always necessary as 1S antibonding molecular orbital is lower in energy as compared to 2S bonding MO If electron jumps from 1S ABMO to 2S BMO  then BOND ORDER willhence bond will become stronger increase σ(1s) &lt;σ∗(1s) &lt; σ(2s) &lt;σ∗(2s) &lt; π(2px) = π(2py)