Additions and Corrections-Reactivity of Ionic Clusters with

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The Journal of Physical Chemistry, Vol. 90, No. 22, 1986

Additions and Corrections

ADDITIONS AND CORRECTIONS

1986, Volume 90

M. L. Mandich,* W. D. Reents, Jr.,* and V. E. Bondybey*: Reactivity of Ionic Silicon Clusters with Methylsilane Studied by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Pages 2315-2319. The absolute reaction rates listed in the previously published version of Table I are in error because of a pressure miscalibration. The correct rates are given in Table I published here and are obtained by multiplying the previous rates by 7.5. This correction brings the absolute reaction rate for Si+ with CH,SiH, to 75% of the Langevin rate. The remainder of the discussion is unaffected by these changes. TABLE I: Cluster Size Dependence of the Rate Constants for the Reaction of Si,' with CHSMj and Comparisons with Cluster Binding Energies and Fragmentation Energies" cluster binding fragmentation cluster reaction rate,b energy,' energy,' eV, for ion cm3 molecule-I s-I eV/atom Si.' Si + Si,,+ Si+ 13 X Siz+ (3.8 f 0.8) X 1.9 3.7 Si3+ (5.7 f 0.5) X 2.6 4.0 Si4+ (1.2 f 0.2) x 3.3 5.5 Si5+ (2.3 f 0.2) X 3.38 3.4 Si6+ 19.0 X 3.73 5.2 Si7+ 1 5 5 x 1 0 - l ~ (3.76) 4.1

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"From ab initio electronic structure calculations in ref 12a of the energy required to separate a Si,+ cluster into ( n - 1)Si + Si'. In this work, the binding energy for Si,' was approximated. bRate constants were determined from slopes of In [Z(Si,')] vs. time; all semilog plots were single exponential. Decay rate measurements were duplicated at differing pressures for Si2-7'. (Pressures measured with the BayardAlpert ionization gauge were corrected for instrumentation effects and sensitivity to CH3SiH3 relative to CH4.16*35)The decay rates were measured several different times for Si,-7'. The range of values for the rate constant for these runs was used to determine the tabulated errors. Note that the listed errors do not account for possible error in the pressure correction factor which may be off by up to a factor of three. This would change the rate constants for the various clusters in absolute value but leave them unchanged relative to each other.