IDENTIFICATION OF ADSORBED BENZYL ON PT(111) USING D(2)-BTPDS

It is shown that adsorbed benzyl (C6H5CH2,a) can be identified and quantified on Pt(111) using D2-BPTDS. This variation of bismuth postdosing thermal desorption mass spectroscopy (BPTDS) involves the addition of deuterium at 100 K before interrogating the adlayer by BPTDS. (A normal BPTDS analysis itself simply involves vapor depositing a monolayer of bismuth to an adlayer at 100 K before TDS.) The net result here is that adsorbed benzyl in the adlayer is quantitatively deuterated via C6H5CH2,a + D(a) --> C6H5CH2D. This gives rise to a sharp, peak for toluene-d1 at approximately 200 K in the TDS spectrum (or, more precisely, in the D2-BPTDS spectrum). This result helps generalize our observation that adsorbed molecular fragments which are missing only one hydrogen atom can be identified by deuteration in D2-BPTDS. It is also shown here that adsorbed toluene (C6H5CH3,a) can be identified and quantified by normal BPTDS and D2-BPTDS. This further generalizes the application of BPTDS in the identification and quantitation of adsorbed molecules.