The quantum yield for formation of 3-methylcyclobutene from E-1,3-pentadiene by 254 nm radiation is ten times greater than for cyclization of the Z-isomer. 1,3-Dimethylcyclopropene is also formed but...

The quantum yield for formation of 3-methylcyclobutene from E-1,3-pentadiene by 254 nm radiation is ten times greater than for cyclization of the Z-isomer. 1,3-Dimethylcyclopropene is also formed but the difference
 in for this reactions is only a factor of two. Offer an explanation for these differences in terms of energy surfaces that are involved.