( ( ( ( ( ( ( The ( excess energy ) ) ( of ( the ( excited state ) ) ) ) ( is ( ( ( emitted ( as light ) ) , ) ( as ( ( the electrons ) ( descend ( to ( lower-energy states ) ) ) ) ) ) ) ) , ) and ) ( ultimately ( , ( ( the ground ) state ) ) ) ) . )
(ROOT (S (S (NP (NP (DT The) (JJ excess) (NN energy)) (PP (IN of) (NP (DT the) (VBN excited) (NN state)))) (VP (VBZ is) (VP (VBN emitted) (PP (IN as) (NP (NN light))) (, ,) (PP (IN as) (NP (NP (DT the) (NNS electrons)) (VP (VBN descend) (PP (TO to) (NP (JJ lower-energy) (NNS states))))))))) (, ,) (CC and) (S (ADVP (RB ultimately)) (, ,) (NP (DT the) (NN ground)) (VP (VBP state))) (. .)))
The excess energy of the excited    state is emitted as light, as the electrons descend to lower-energy states,    and ultimately, the ground state.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NNS electrons)) (VP (VB return) (PP (TO to) (NP (DT a) (JJR lower) (NN energy) (NN level)))))) (, ,) (NP (PRP they)) (VP (VBP emit) (NP (NP (DT the) (JJ excess) (NN energy)) (PP (IN in) (NP (NP (DT the) (NN form)) (PP (IN of) (NP (NN light))))))) (. .)))