( They ( ( ( ( ( ( collide ( with ( gas atoms ) ) ) and ) ( ionize ( those atoms ) ) ) , ) ( releasing ( ( more charged ) particles ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VP (VBP collide) (PP (IN with) (NP (NN gas) (NNS atoms)))) (CC and) (VP (VBP ionize) (NP (DT those) (NNS atoms))) (, ,) (S (VP (VBG releasing) (NP (ADJP (RBR more) (VBN charged)) (NNS particles))))) (. .)))
They collide with gas atoms and ionize those atoms, releasing more charged particles.
(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)))))))