Chandrasekhar N, Krebs P, Unterreiner A-N
Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Universität Karlsruhe (TH), Kaiserstrasse 12, D-76128 Karlsruhe, Germany.
J Chem Phys. 2006 Oct 28;125(16):164512. doi: 10.1063/1.2362822.
Solvated electrons in glycerol were generated via a resonant one-photon photodetachment of the charge-transfer-to-solvent (CTTS) band of I- in glycerol (Gl) after irradiation with a 248 nm excimer laser. Optical absorption spectra of solvated electrons (esolv-) in Gl were recorded as a function of temperature (381<or=T<or=505 K). The observed redshift of the absorption maximum, homegamax, yields a temperature coefficient d(homegamax)/dT=-(2.67+/-0.07)x10(-3) eV K-1. For solutions with a concentration c(I-) approximately 10(-3)M, the absorbance of esolv- at homegamax increases by a factor of about 65 when the temperature is raised from 329 to 536 K. This effect can be partially explained by a temperature-dependent redshift of the CTTS spectrum of I- in Gl with respect to the laser wavelength. The main contribution to the increasing yield of esolv- is determined by diffusion controlled escape dynamics of the electron in the contact pair (I:e-)solv which is formed very fast during the detachment process. At room temperature no absorption of esolv- (absorbance<1.0x10(-3)) could be observed which is probably a result of an extremely small self-diffusion coefficient of Gl (a factor of 1250 lower than that of water at 298 K). The results are compared with a previous study of I- in ethylene glycol.
在用248nm准分子激光辐照后,通过甘油中I⁻的电荷转移到溶剂(CTTS)带的共振单光子光解离,在甘油中产生了溶剂化电子。记录了甘油中溶剂化电子(esolv⁻)的光吸收光谱随温度(381≤T≤505K)的变化。观察到的吸收最大值红移,即homegamax,得出温度系数d(homegamax)/dT = -(2.67±0.07)×10⁻³eV K⁻¹。对于浓度c(I⁻)约为10⁻³M的溶液,当温度从329K升高到536K时,esolv⁻在homegamax处的吸光度增加约65倍。这种效应可以部分地由甘油中I⁻的CTTS光谱相对于激光波长的温度依赖性红移来解释。esolv⁻产率增加的主要贡献由电子在接触对(I:e⁻)solv中的扩散控制逃逸动力学决定,该接触对在解离过程中很快形成。在室温下未观察到esolv⁻的吸收(吸光度<1.0×10⁻³),这可能是由于甘油的自扩散系数极小(比298K时水的自扩散系数低1250倍)的结果。将这些结果与先前对乙二醇中I⁻的研究进行了比较。