Pulse radiolysis of sodium formate aqueous solution up to 400 °C: Absorption spectra, kinetics and yield of carboxyl radical CO2−

Sodium formate neutral aqueous solutions saturated with N2O were studied by pulse radiolysis techniques from room temperature to 400 °C. The absorption spectra of CO2− show a red shift from λmax=235 nm at 25 °C to 280 nm at 400 °C. The second-order decay of CO2− is not monotonically temperature-dependent: the rate constant (2k/ε) slightly increases with temperature up to 200 °C, then decreases to a valley at 300 °C, and it sharply increases again for temperature >350 °C. Gε(CO2−) increases with temperature from room temperature to 400 °C. Significant density effect on Gε(CO2−) is found at 400 °C. Assumed ε(CO2−) is independent on temperature, at 400 °C, the density dependence of G(CO2−) in the presence of N2O agrees well with that of {G(eaq−)+G(H)+G(OH)}.