Free radical motion in super critical fluids probed by EPR spectroscopy

被引:20
作者
Batchelor, SN [1 ]
机构
[1] Univ Zurich, Inst Phys Chem, CH-8057 Zurich, Switzerland
来源
JOURNAL OF PHYSICAL CHEMISTRY B | 1998年 / 102卷 / 03期
关键词
D O I
10.1021/jp972346a
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
EPR spectra of the nitroxide radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) are reported in super critical and in liquid n-hexane and ethanol for 25-200 bar and 295-600 K. At low radical concentration (<10(-5) M) the line width is controlled by the spin-rotation interaction and is quantitatively predicted by liquid-phase theory for solvent densities rho greater than the critical density rho(c). Deviations at lower densities are assigned to clustering effects and the crossover to gas-phase behavior. Rate constants for Heisenberg spin exchange ([TEMPO] > 10(-3) M) up to 580 K are also reported. They again follow liquid-phase theory for rho > rho(c). Deviations at low densities may be explained by a gas-phase behavior without clustering effects.
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页码:615 / 619
页数:5
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