We have studied the dissociation dynamics of Mg2CH4+ ion-molecule clus
ters through mass-resolved photodissociation spectroscopy, coupled wit
h translational energy spectroscopy. We have observed distinct molecul
ar absorption bands in the red (690-615 nm) and green (580-545 nm) spe
ctral regions. Mg+ is the dominant fragmentation product in each band,
We observe a significant energy release into relative translation and
a pronounced photofragment anisotropy (beta >0), consistent with a ra
pid dissociation. Based on the observed anisotropy and the result of a
n ab initio structure calculation, we assign the red band to the paral
lel transition 2(2)A'<--1(2)A' and the green band to a combination of
1 (2)A''<--1 (2)A' and 3 (2)A'<--1 (2)A' transitions, all in C-s, symm
etry. These results are compared with earlier results from the photodi
ssociation spectroscopy of the more strongly bound Mg2CO2+ and Mg2H2O bimolecular complexes. (C) 1997 American Institute of Physics.