Wj. Knott et al., THE HYDROGEN-ATOM ABSTRACTION REACTION CO-]HCO++H - TRANSLATIONAL ANDINTERNAL ENERGY-DEPENDENCE OF THE INTEGRAL CROSS-SECTION(H2), The Journal of chemical physics, 108(2), 1998, pp. 527-533
The widely accepted model descriptions of ion-molecule reactions sugge
st identical rate constants for the title reaction and the analogous,
isoelectronic system N-2(+)+H-2, which has been the topic of a previou
s publication from this laboratory. A comparison of both data sets, ho
wever, reveals substantial disagreement which we attribute to the abse
nce of energetic resonances between the reagents which characterized t
he N-2(+)/H-2 system. Resonantly enhanced photoionization was exploite
d to accomplish the state-specific preparation of CO+ (X (2) Sigma(+),
upsilon(+) = 0,1). A monoenergetic beam of vibrationally selected ion
s, tuned within the range 0.01 eV less than or equal to E(cm)less than
or equal to 10 eV, transits a scattering chamber which confines the n
eutral, H-2. The title reaction was the only channel observed-no evide
nce of charge transfer or dissociative ionization could be detected. T
he hydrogen atom transfer turns out to proceed directly. The reactive
cross section fails to show the E-1/2 dependence indicative of collisi
on determined processes. The experimental data are perfectly mimicked
by an expanded Langevin model which includes additional attractive pot
ential terms. In contrast to the N-2(+)/H-2 case, vibrational excitati
on does not affect the rate of the reaction. (C) 1998 American Institu
te of Physics.