FIG. 5: (a)-(h) illustrate the calculated atomic displacements for the frequencies ω$_{1}$ - ω$_{8}$ . turned into the SCH$_{2}$COO − molecules. The frequency ω$_{8}$ (1711cm − $^{1}$, 1733cm − $^{1}$) corre- sponds to the C=O stretching vibration for the HSCH$_{2}$COOH on the Au(111) substrate (Fig. 5h). Thus the above frequency comparison suggests that after the HSCH$_{2}$COOH molecules deposited on the Au(111) surface, some stay intact on the surface, the rest have turned into SCH$_{2}$COOH (via dissociation), HSCH$_{2}$COO − (deprotonation) and SCH$_{2}$COO − (dissociation and deprotonation). 15