## 3 Results and Discussion
### TPPE Characteristics for Sample A and Sample C and Their Relation to the Properties of Liquids
Figures 10 and 11 show the relation between the TPPE characteristics and the properties of the liquids: \(N_{\rm{Tmax}}\)a, \(\Delta\)Eu\({}_{\rm{Up1}}\), \(AN\), and \(1/\varepsilon/\varepsilon_{0}\) for sample A, and \(N_{\rm{Tmax}}\)c, \(\Delta\)Ec\({}_{\rm{Up1}}\), \(AN\), and \(1/\varepsilon/\varepsilon_{0}\) for sample C, respectively. At first, in Figure 12, we consider the adsorption of the molecules of alcohols and water on the surface hydroxyl group (Cu-OH) at the surface. It should be noted that Cu(OH)\({}_{2}\) has been reported to play an initial key role in growth of the corrosion layer [25]. We consider that the acid-base property of Cu-OH can be determined by the electron density of the oxygen atom of the Cu-OH on the surface. We think that the oxide film of sample A is much thinner than that of sample C. Due to the bias of the negative potential and the light irradiation during the TPPE measurement, it is  
Figure 9: Relation between the reciprocal of dielectric constant (\(\varepsilon/\varepsilon_{0}\)) and acceptor number (\(AN\)) of the liquids. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Liquids Used for Abrading** & **Acceptor Number (a)** & **Donor Number (a)** & **Dielectric Constant** & **Reciprocal of** \\
**and Ultrasonic Cleaning** & & & **(25 \({}^{\circ}\)C) (d)** & **Dielectric Constant** \\ \hline  & \(AN\) & \(DN\) & \(\varepsilon/\varepsilon_{0}\) & \(1/(\varepsilon/\varepsilon_{0})\) \\ \hline (1) Water (H\({}_{2}\)O) & 54.8 & 18.0 & 78.39 & 0.0128 \\ \hline (2) Methanol (CH\({}_{3}\)OH) & 41.3 & 20.0 & 32.70 & 0.0306 \\ \hline (3) Ethanol (C\({}_{2}\)H\({}_{5}\)OH) & 37.1 & 19.0 & 24.55 & 0.0407 \\ \hline (4) 2-Propanol (CH\({}_{3}\))\({}_{2}\)CHOH) & 33.5 (b) & 21.1 (b) & 19.92 & 0.0502 \\ \hline (5) 1-Propanol (C\({}_{3}\)H\({}_{7}\)OH) & & & 20.33 & 0.0492 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Relation between acceptor number, donor number, and dielectric constant of liquids. considered that the electron density of the oxygen of sample A is low, but that of sample C is high, with the former acting as an acid and the latter as a base. **Scheme 1. ** The solvation between triethylphosphine oxide (C\({}_{2}\)H\({}_{5}\))\({}_{3}\)P=O and solvent molecule (S), changing charge distribution on P and O atoms and its correspondence to the adsorption of the alcohols and water on the surface hydroxyl group (-Cu-OH). Figure 10: [Sample A] TPPE characteristics of copper sheets subjected to 10-minute abrasion in liquids and the property of liquids: (**a**) relation between the maximum value of \(N_{\text{T}}\)(\(N_{\text{Tmax}}\)a) during the Up1 scan and the acceptor number (\(AN\)) of the liquids; (**b**) relation between the activation energy of photoelectron emission (\(\Delta\)Ea\({}_{\text{Up1}}\)) during Up1 scan and the acceptor number (\(AN\)) of the liquids; (**c**) relation between \(\Delta\)Ea\({}_{\text{Up1}}\) and the reciprocal of dielectric constant (\(\varepsilon/\varepsilon_{0}\)) of the solvents; (**d**) relation between the value of \(N_{\text{Tmax}}\)a and \(\Delta\)Ea\({}_{\text{Up1}}\). The data come from Table 1. We used the same color lines in (**a–d**) of Figures 10 and 11 for comparison. As a result, the -Cu-OH of sample A more strongly interacts with more basic liquid molecules, while that of sample C more strongly acts with more acidic liquid molecules. Figure 12 shows the orientation of the electric dipole produced by the adsorbed molecule. For the property of the liquids, we used [PERSON]'s acceptor number (\(AN\)), representing the basicity of the liquid molecules: (CH\({}_{3}\))\({}_{2}\)CHOH (33.5), C\({}_{2}\)H\({}_{5}\)OH (37.1), CH\({}_{3}\)OH (41.3), and H\({}_{2}\)O (54.8). This was well related to the TPPE characteristics. With sample A, the values of \(N_{\rm Tmax}\)a and \(\Delta\)Eu\({}_{\rm Up1}\) both increased with increasing \(AN\) (Table 1 and Figure 10). On the other hand, with sample C, the values of \(N_{\rm Tmax}\)c and \(\Delta\)Eu\({}_{\rm Up1}\) both decreased with increasing \(AN\) (Table 2 and Figure 11).