Light expression to separate emission light groups in AOVs

Hi! I have this Arnold Atmosphere Volume pass which, in Arnold, is stored in the emission AOV since it's not a 'real' volume. I've tried the LPE **C[LO].*<L.'lamp'>** ('lamp' is the ligt group name) but it doesn't work. How could I separate these diferent types of light in the emission pass? Thank you in advance!!