[1] Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA
[2] Univ Denver, Dept Phys, Denver, CO 80208 USA
[3] NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA
[4] Univ Wollongong, Dept Chem, Wollongong, NSW 2522, Australia