The increased energy is sufficient to remove the lone remaining electron in the He II, transforming it into He III (second ionization). This causes the opacity of the He layer to increase and the energy flux from the interior of the star is effectively absorbed. The temperature of the star's core increases, which causes it to expand.
The increased energy is enough to remove the last electron in the He II state, resulting in the formation of He III (second ionization). This results in an increase in the opacity of the He layer and a reduction in the energy flux from the star's interior. As a result, the core temperature rises, causing the star to expand.