How Hot are Your Ions Really? A Threshold Collision-Induced Dissociation Study of Substituted Benzylpyridinium "Thermometer" Ions.

The first absolute experimental bond dissociation energies (BDEs) for the main heterolytic bond cleavages of four benzylpyridinium "thermometer" ions are measured using threshold collision-induced dissociation in a guided ion beam tandem mass spectrometer. In this experiment, substituted benzylpyridinium ions are introduced into the apparatus using an electrospray ionization source, thermalized, and collided with Xe at varied kinetic energies to determine absolute cross-sections for these reactions. Various effects are accounted for, including kinetic shifts, multiple collisions, and internal and kinetic energy distributions.

Hydrated copper ion chemistry: guided ion beam and computational investigation of Cu2+(H2O)n (n = 7-10) complexes.

Cross sections for the threshold collision-induced dissociation of Cu(2+)(H(2)O)(n), where n = 8 - 10, are measured using a guided ion beam tandem mass spectrometer. The primary dissociation pathway is found to be loss of a single water molecule followed by the sequential loss of additional water molecules until n = 8, at which point charge separation to form CuOH(+)(H(2)O)(4) (+) H(+)(H(2)O)(3) is observed to occur at a slightly lower energy than loss of a water molecule. Competition from charge separation prohibits the formation of appreciable amounts of the n = 7 or smaller complexes as reactants in the source.

Guided ion beam studies of the collision-induced dissociation of CuOH+(H2O)n (n = 1-4): comprehensive thermodynamic data for copper ion hydration.

Threshold collision-induced dissociation (TCID) using a guided ion beam tandem mass spectrometer is performed on CuOH(+)(H2O)n where n = 1-4. The primary dissociation pathway for the n = 2-4 reactants consists of loss of a single water molecule followed by the sequential loss of additional water molecules at higher collision energies. The n = 1 reactant departs from this trend by losing the OH ligand and the H2O ligand competitively.

Direct-dynamics study of the F + CH4, C2H6, C3H8, and i-C4H10 reactions.

We present a theoretical study of the dynamics of the first few members of the F + alkane --> HF + alkyl family of reactions (alkane = CH(4), C(2)H(6), C(3)H(8), and i-C(4)H(10)). Quasiclassical trajectories have been propagated employing a reparameterized semiempirical Hamiltonian that was derived in this work based on ab initio information of the global potential-energy surfaces of all reactions studied. The accuracy of the Hamiltonian is probed via comparison of the calculated dynamics properties with experimental results in the F + CH(4) --> HF + CH(3), F + CD(4) --> DF + CD(3), and F + C(2)H(6) --> HF + C(2)H(5) reactions.