Abstract
Significant improvements to the single crystal adsorption calorimeter
(SCAC) of Borroni-Bird and King are described. The calorimeter comprises
a pulsed molecular beam source, an ultrathin single crystal and an
infrared detector. It is calibrated using a chopped laser beam, and
the amount of gas adsorbed or reacted per pulse is measured using
the King and Wells reflection detector technique, Refinements in
the molecular beam system, the optical calibration system, flux calibration
system and sticking probability measurement technique have been made.
The calorimeter response is accurately linear over a useful energy
range; the detection limit is estimated as 10 kJ mol(-1) and the
accuracy in heats of adsorption for heats above similar to 80 kJ
mol(-1) is estimated as similar to 6%, Comparisons of calorimetric
heats with isosteric heats and with desorption energies obtained
for reversible systems, such as CO on Ni and Pt single crystal surfaces,
generally yield good agreement and give support to the estimate for
the absolute accuracy of the instrument.
Users
Please
log in to take part in the discussion (add own reviews or comments).