( They ( ( ( are eventually ) ( ( lost either ) ( ( ( ( when ( they ( collide ( with ( ( background ( gas atoms ) ) ( present ( in ( the ( vacuum chamber ) ) ) ) ) ) ) ) ) , ) or ) ( when ( ( two ( trapped atoms ) ) ( ( collide ( in ( such ( a way ) ) ) ) ( that ( ( ( one or ) both ) ( ( ( flips over ) and ) ( goes ( into ( the ( untrapped state ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP are) (ADVP (RB eventually)) (VP (VBN lost) (ADVP (RB either)) (SBAR (SBAR (WHADVP (WRB when)) (S (NP (PRP they)) (VP (VBP collide) (PP (IN with) (NP (NP (NN background) (NN gas) (NNS atoms)) (ADJP (JJ present) (PP (IN in) (NP (DT the) (NN vacuum) (NN chamber))))))))) (, ,) (CC or) (SBAR (WHADVP (WRB when)) (S (NP (CD two) (JJ trapped) (NNS atoms)) (VP (VBP collide) (PP (IN in) (NP (PDT such) (DT a) (NN way))) (SBAR (IN that) (S (NP (NP (CD one)) (CC or) (NP (DT both))) (VP (VP (VBZ flips) (PRT (RP over))) (CC and) (VP (VBZ goes) (PP (IN into) (NP (DT the) (JJ untrapped) (NN state))))))))))))) (. .)))
They are eventually lost either when they collide with background gas atoms present in the vacuum chamber, or when two trapped atoms collide in such a way that one or both flips over and goes into the untrapped state.
(ROOT (S (PP (IN Within) (NP (DT a) (NN substance))) (, ,) (NP (NP (NNS atoms)) (SBAR (WHNP (WDT that)) (S (VP (VP (VBP collide) (ADVP (RB frequently))) (CC and) (VP (VBP move) (ADVP (RB independently)) (PP (IN of) (NP (CD one) (DT another)))))))) (VP (VBP are) (ADJP (ADJP (RBS most) (JJ likely)) (PP (IN in) (NP (DT a) (NN gas)))))))