Photodissociation spectroscopy of Mg2CH4+

We have studied the dissociation dynamics of Mg2CH4+ ion-molecule clusters through mass-resolved photodissociation spectroscopy, coupled with translational energy spectroscopy. We have observed distinct molecular absorption bands in the red (690-615 nm) and green (580-545 nm) spectral 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 rapid dissociation. Based on the observed anisotropy and the result of an ab initio structure calculation, we assign the red band to the parallel 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, symmetry. These results are compared with earlier results from the photodissociation spectroscopy of the more strongly bound Mg2CO2+ and Mg2H2O+ bimolecular complexes. (C) 1997 American Institute of Physics.