Vibrational linewidths of adsorbed molecules: Experimental considerations and results

Al72 J.K. BLUM Fachbereich Chemie, Unioersitiit Oldenburg, D-2900 Oldenburg, Fed. Rep. of Germany Received

5 September

1986; accepted

for publication

4 November

1986

Faujasite supported nickel dispersions were prepared having particle sizes of monomodal (average particle size: l-2 nm), bimodal (average particle sizes: 1-2 and 4 nm) and polymodal distribution. AI1 types of dispersion were characterized by electron optical methods and ferromagnetic resonance absorption. The appearance of an additional subsidiary low field peak in the sample obtained by reduction with a mixture of hydrogen and carbon monoxide is related to the presence of surface nickel carbides.

Surface Science 183 (1987) 226-250 North-Holland, Amsterdam

226

VIBRATIONAL LINEWIDTHS OF ADSORBED MOLECULES: EXPERIMENTAL CONSIDERATIONS AND RESULTS R.G. TOBIN * Department of Physics, University of California, and Materials Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA

and Molecular Reseurch Division,

Received

1986

30 July 1986; accepted

for publication

14 November

The current understanding of the causes of vibrational line-broadening in adsorbates is discussed, with particular emphasis on experimental considerations. Recent experimental determinations of line-broadening mechanisms are reviewed. While there has been great progress in the theoretical understanding of line-broadening by energy and phase relaxation, it remains difficult to determine experimentally the relative importance of the various proposed mechanisms. Inhomogeneous broadening, which is certainly important in many cases, has received little theoretical attention.

Surface Science 183 (1987) 251-262 North-Holland, Amsterdam

251

PHASE TRANSITION: CONDENSATE-TWO-DIMENSIONAL IN SUPER THIN LAYERS OF Cu AND Ag ADSORBED ON THE Mo(Ol1) FACE J. KOLACZKIEWICZ

GAS

Institute of Experimental Physics, University of Wroclaw, ul. Cybulskzego 36, PL-50-205 Wroclaw, Poland Received

30 April 1986; accepted

for publication

14 November

1986

The phase transition: condensate-two-dimensional gas was found in super thin, 0 < 0.2 ML, layers of Cu and Ag adsorbed on the Mo(001) face. Critical parameters T, and 0, were determined. Good agreement of the experimental coexistence curve T(0) and the theoretical one described by the van der Waals equation or the quasichemical approximation was found. Based on the Clausius-Clapeyron equation the heat of two-dimensional evaporation was calculated.