Technetium-99m (99mTc^{99\text{m}}\text{Tc}99mTc) is a metastable nuclear isomer widely used as a radioactive tracer in medical imaging. When a nucleus of 99mTc^{99\text{m}}\text{Tc}99mTc transitions to its ground state, 99Tc^{99}\text{Tc}99Tc, it undergoes gamma decay by emitting a high-energy photon.
State the change, if any, in the energy of the nucleus as a result of this transition.