## 3 Results and Discussion  
### PE Stimulation Spectra and TPPE Plot  
Figure 2 shows typical PE stimulation spectra observed during wavelength scans in the temperature increase process for copper samples abraded in CH\({}_{3}\)OH [26] and abraded and cleaned only in C\({}_{2}\)H\({}_{5}\)OH. The intensity of PE increases progressively and reaches a maximum, followed by a decrease with decreasing wavelength of the light (or increasing photon energy). An emission peak appears around 220-200 nm. In Figure 2(1), the PE intensity of the peak in the PE stimulation spectrum decreases and interestingly shifts to a shorter wavelength with increasing abrasion time. In Figure 2(2), the emission peak of all the spectra yields the maximum at 250 \({}^{\circ}\)C. We call the total number of emitted electrons in the PE stimulation spectra PE total count (\(N_{\text{T}}\)). Figure 1: The temperature-programmed photoelectron emission (TPPE) measurement apparatus (The arrows written in the figure indicate the inlet and outlet of Q gas and constant temperature water, and the direction of irradiation of photons (\(h\
u\)) and collection of emitted electrons). Figure 3 shows the TPPE plots of \(N_{\rm T}\) vs. temperature during the 1 st and 2 nd temperature increase and subsequent temperature decrease processes for copper samples (sample A) abraded for 10 min in various environments: (1) H\({}_{2}\)O, (2) CH\({}_{3}\)OH, (3) C\({}_{2}\)H\({}_{5}\)OH, (4) (CH\({}_{3}\))\({}_{2}\)CHOH, (5) C\({}_{3}\)H\({}_{7}\)OH, and (6) ambient air. This plot is called the TPPE plot. It should be noted that in the TPPE plot, the corrected values of \(N_{\rm T}\) were used by deducting the temperature increase and subsequent temperature decrease processes. Figure 2: Examples of typical PE stimulation spectra in the temperature increase process: (**1**) Effect of abrasion time on PE measurement at 250 \({}^{\circ}\)C for copper samples abraded in CH\({}_{3}\)OH. Abrasion time: (a) 5 min, (b) 10 min, and (c) 30 min. (2) Effect of ultrasonic cleaning only and abrasion in C\({}_{2}\)H\({}_{5}\)OH on PE measurement for copper samples: (\(\alpha\)) cleaning for 5 min and (\(\beta\)) abrasion for 10 min. the natural count (1000 counts). The TPPE plot in the Up1 process exhibits a markedly different behavior from that in other processes; that is, in each environment, the value of \(N_{\rm T}\) remains low at the initial stage, starts to increase at 100 \({}^{\circ}\)C, and reaches a maximum at 250 \({}^{\circ}\)C, followed by a decrease, except for the TPPE plot for C\({}_{3}\)H\({}_{7}\)OH, which gives the maximum at 100 \({}^{\circ}\)C, being completely different from the other environments. Therefore, we have paid much attention to the TPPE plot in the Up1 process. For the abraded Cu samples, the effect of the abrasion periods (5, 10, and 30 min) on the TPPE characteristics is featured as follows [26]. In the cases of H\({}_{2}\)O, CH\({}_{3}\)OH, and C\({}_{2}\)H\({}_{5}\)OH, there is little difference in the \(N_{\rm T}\) values at low temperature, but the growth of \(N_{\rm T}\) values with increasing temperature is suppressed with an increase in the abrasion period, producing the most pronounced difference at 250-300 \({}^{\circ}\)C. The values of \(N_{\rm T}\) become very small at 350 \({}^{\circ}\)C. A striking observation in these cases is that the \(N_{\rm T}\) value yields a distinct maximum at 250-300 \({}^{\circ}\)C. This maximum tends to appear at a higher temperature, and clearly, the level of the maximum \(N_{\rm T}\) for CH\({}_{3}\)OH and C\({}_{2}\)H\({}_{5}\)OH lowers with increasing abrasion periods, although in the case of H\({}_{2}\)O, the maximum decreases in the order 10 min > 5 min > 30 min. In the case of the abraded samples, two small broad peaks appear around 100 \({}^{\circ}\)C and 250-300 \({}^{\circ}\)C for C\({}_{3}\)H\({}_{7}\)OH, and one peak appears at 300 \({}^{\circ}\)C for (CH\({}_{3}\))\({}_{2}\)CHOH, resulting in a very small effect of the abrasion period on the TPPE plot.