( ( Only ( at ( ( ( the temperature ) ( of ( absolute zero ) ) ) ( -LRB- ( ( ( -273 degrees ) C ) -RRB- ) ) ) ) ) ( ( ( does ( molecular activity ) ) ( ( ( cease and ) IR ) ( radiation ( ( no longer ) emit ) ) ) ) . ) )
(ROOT (SINV (ADVP (RB Only) (PP (IN at) (NP (NP (DT the) (NN temperature)) (PP (IN of) (NP (JJ absolute) (CD zero))) (PRN (-LRB- -LRB-) (NP (NP (CD -273) (NNS degrees)) (NP (NNP C))) (-RRB- -RRB-))))) (VBZ does) (NP (JJ molecular) (NN activity)) (VP (VB cease) (CC and) (VB IR) (NP (NP (NN radiation)) (ADJP (ADVP (RB no) (RBR longer)) (JJ emit)))) (. .)))
Only at the temperature of absolute zero (-273 degrees C) does molecular activity cease and IR radiation no longer emit.
(ROOT (S (NP (NP (DT The) (NN temperature)) (SBAR (WHPP (IN at) (WHNP (WDT which))) (S (NP (DT all) (JJ molecular) (NN motion)) (VP (VBZ has) (VP (VBN ceased)))))) (VP (VBZ is) (VP (VBN called) (NP (JJ absolute) (NN zero)))) (. .)))