Electron attachment to NO was studied in supercritical ethane at 33, 3
7, and 47 degrees C as a function of pressure (35-110 bar). The rate c
onstant for electron attachment increases with increasing pressure at
all temperatures studied. The most dramatic increases are observed nea
r the critical pressure. The activation volume for this reaction is ne
gative and quite large in magnitude, especially in this region. The ac
tivation volume depends on the isothermal compressibility. The results
are compared to volume changes predicted by a compressible continuum
model.