Threshold photoelectron-photoion coincidence spectroscopy: dissociation dynamics and thermochemistry of Ge(CH3)4, Ge(CH3)3Cl, and Ge(CH3)3Br

Threshold photoelectron-photoion coincidence spectroscopy (TPEPICO) has been used to investigate the gas-phase ionic dissociation energies and thermochemistry of Me4Ge and Me3GeX, (Me = methyl; X = Cl, Br) molecules. The 0 K dissociation onsets for these species have been measured from the breakdown diagram and the ion time-of-flight distributions, which were modeled with the statistical RRKM theory and DFT calculations. The measured 0 K dissociative photoionization onsets were as follows: Me3Ge+ + Me (9.826 +/- 0.010 eV); Me3Ge+ + Cl (10.796 +/- 0.040 eV); Me3Ge+ + Br (10.250 +/- 0.011 eV); Me2GeCl+ + Me (10.402 +/- 0.010 eV); and Me2GeBr+ + Me (10.333 +/- 0.020 eV). These onsets were used to obtain new values for delta(f)H(degrees)298 (in kJ/mol) of the neutral molecules Me3GeCl (-239.8 +/- 5.7) and Me3GeBr (-196.5 +/- 4.3), and also for the following ionic species: Me3Ge+ (682.3 +/- 4.1), Me2GeCl+ (621.1 +/- 5.8), and Me2GeBr+ (657.8 +/- 4.7).