[The effect of temperature on the behavior of aminobenzoic acid on silver surface]

SERS spectra of p-Aminobenzoic Acid (PABA) and o-Aminobenzoic Acid (OABA) absorbed on a silver surface, roughened by nitric acid, have been measured with a Renishaw Raman microprobe spectrometer(lambda = 632.8 nm) at different temperature, which ranged from 30 degrees C to -190 degrees C and from -190 degrees C to 30 degrees C. Some reversible changes in some band positions have been observed. The results indicated that if the adsorbates were enhanced by chemical mechanism and the molecules lie flat on surface, e.g. p-Aminobenzoic Acid molecule, temperature had no effect on their orientation. However, the vibrational frequencies enhanced by electromagnetic mechanism shifted as temperature changed, e.g. the vibration of NH2 in o-Aminobenzoic. The fact was that temperature had effect on the orientation of the molecules.