Applicability of reaction rate in gas phase data to supercritical water region

研究OH自由基在高温水中的反应速率，最直接的方法是观察OH自由基本身的瞬态吸收。在室温下，有几个这样的直接测量的演示，然而，在高温条件下的例子很少。在直接紫外吸收测量中，蓝宝石窗口的吸收阻止了OH信号的测量。通过减去蓝宝石窗口信号来确定由于OH自由基引起的实际吸收强度。高温水中OH自由基的吸收光谱发生蓝移。OH自由基在250 nm处的吸收系数随温度的升高而减小。在室温下，OH自由基的吸收系数已知为500。在300 ℃时，我们发现吸收系数下降到200。速率之后是高达125 ℃的Arrhenius温度依赖性。然而，在125 ℃以上，反应速率与水温无关。在125 ℃下的反应速率为1 × 10 - <10>4 M/<-1>s<-1>。

To study reaction rate of OH radical in high temperature water, the most direct method is to observe the transient absorption of OH radical itself. At room temperature there are a several demonstrations for such direct measurements, however, there are few example under high temperature conditions. In the direct UV absorption measurements, the absorption by sapphire windows prevents the measurement of OH signal. The actual absorption intensity due to OH radical was determined by subtraction of the sapphire window signals. The absorption spectra of OH radical in high temperature water shifted to blue. The absorption coefficient of OH radical at 250 nm decreased with increasing the temperature. At room temperature, the absorption coefficient of OH radical is known as to be 500. At 300 C, we found that the absorption coefficients decreased to 200.The temperature dependence of OH radical reaction rate was examined. The rates are followed by the Arrhenius temperature dependence up to 125 C. Above 125 C, however, the reaction rates are independent on the water temperature. The reaction rate at 125 C was 1x10^<10> M^<-1>s^<-1>.