Room-temperature reactions of 46 different atomic cations with N 2 O have been surveyed systematically using an inductively coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. The atomic cations are produced at about 5500 K in the ICP source and are allowed to decay radiatively and thermalize by collisions with Ar and He atoms prior to reaction. Rate coefficients were measured for the reactions of first-row atomic cations from K + to Se + , of second-row atomic cations from Rb + to Te + (excluding Tc + ), and of third-row atomic cations from Cs + to Bi + . Primary reaction channels were observed corresponding to O-atom transfer, N-atom transfer, and N 2 O addition. Periodicities were observed in overall reaction efficiency, and these are scrutinized in terms of overall exothermicity, the presence of an activation barrier in the reaction coordinate, and the overall conservation of spin. N-atom transfer was observed to compete with O-atom transfer in the reactions of N 2 O with La + (4%), Ti + (22%), Zr + (45%), Nb + (35%), Ta + (40%), and Os + (60%). Up to three N 2 O molecules were observed to add sequentially to selected atomic cations as well as several monoxide and dioxide cations. A second O-atom transfer was observed with the group 4, 5, and 6 transition-metal ions (except Mo + ) as well as the third-row cations Re + , Os + , Ir + , and Pt + . The atomic ions W + , Os + , and Ir + formed trioxides in sequential O-atom transfer reactions, and Os + even formed the tetroxide OsO 4 + . Multicollision-induced dissociation studies with Ar buffer gas indicated thermodynamically controlled dissociation of TiO 2 + , ZrO 2 + , HfO 2 + , VO 2 + , NbO 2 + , TaO 2 + , and WO 2 + by the consecutive detachment of O-atoms while CrO 2 + , ReO 2 + , and PtO 2 + decomposed primarily by loss of O 2 molecules.

Reactions of methane have been measured with 59 atomic metal cations at room temperature in helium bath gas at 0.35 Torr using an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. The atomic cations were produced at approximately 5500 K in an ICP source and allowed to decay radiatively and to thermalize by collisions with argon and helium atoms prior to reaction. Rate coefficients and product distributions are reported for the reactions of fourth-row atomic cations from K(+) to Se(+), of fifth-row atomic cations from Rb(+) to Te(+) (excluding Tc(+)), of sixth-row atomic cations from Cs(+) to Bi(+), and of the lanthanide cations from La(+) to Lu(+) (excluding Pm(+)). Two primary reaction channels were observed: C-H bond insertion with elimination of H(2), and CH(4) addition. The bimolecular H(2) elimination was observed in the reactions of CH(4) with As(+), Nb(+), and some sixth-row metal cations, i.e., Ta(+), W(+), Os(+), Ir(+), Pt(+); secondary and higher-order H(2) elimination was observed exclusively for Ta(+), W(+), and Ir(+) ions. All other transition-metal cations except Mn(+) and Re(+) were observed to react with CH(4) exclusively by addition, and up to two methane molecules were observed to add sequentially to most transition-metal ions. CH(4) addition was also observed for Ge(+), Se(+), La(+), Ce(+), and Gd(+) ions, while the other main-group and lanthanide cations did not react measurably with methane.

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