Pyroelectric detector for single-crystal adsorption microcalorimetry: analysis of pulse shape and intensity

In microcalorimetry for measuring heats of adsorption on clean single-crystal surfaces, a pulse of gas from a molecular beam adsorbs on an ultrathin single crystal's surface, causing a measurable transient heat input and temperature rise. One new and sensitive method of heat detection uses a 9 mu m pyroelectric polymer ribbon, which is mechanically driven to make a gentle mechanical/thermal contact to the back of the single-crystal sample during measurement (J.T. Stuckless, N.A. Frei, C.T. Campbell, A novel single-crystal adsorption calorimeter and additions for determining metal adsorption and adhesion energies, Rev. Sci. Instr. 69, 1998, 2427-2438). Here we describe simulations of the signal pulse shape and an analysis of absolute signal intensities, based on system parameters such as the detector pyroelectric coefficient and thermal conductivities of the detector and sample, in order to understand heat collection efficiency in this and related calorimetric techniques. (C) 2000 Elsevier Science S.A. All rights reserved.