Figure 3
Positive (a,b) and negative (c,d) secondary ion spectra received on the stored sample (‘Cu’) and on the paper (‘paper’) sample are shown in a region of low masses (< 75 amu) and in a region of higher masses (> 300 region). The low mass secondary ion spectra of the Cu sample indicate a rather clean metallic sample with slight contaminations of typical environmental simple hydrocarbons. Some corresponding peaks are also found on the paper, but the observed peak groups differ. In the region of higher masses (> 300 amu), which is significant for more complex organic molecules, the dominant peaks found on the paper at 311, 325 and 383 amu were not found on the Cu sample, which indicates that there is no complex component of the paper material like cellulose molecules transferred to the sample.
