Benzene has been found to capture slowlpar;lsim; 0.3thinsp;eVrpar;electrons in high densities of N2(and Ar) with a rate that increases with increasing N2density and decreasing electron energy at nearhyphen;thermal energies. The dependence of the attachment rate on the N2density and the electron energy has been studied in detail, and a model is presented that accounts for the experimental results. On the basis of this model the autodetachment lifetime ofC6H6hyphen;*has been estimated and found to vary from sim;1 psec at 0.04 eV to sim;0.2 psec at 0.18 eV. From the highhyphen;pressure experiments the ``liquid state behavior'' has been predicted also. The finding that benzene negative ions are formed in the gas phase forces the conclusion that the benzene molecule has a positive (0 eV) electron affinity, (EA)B, contrary to the accepted view that (EA)B0 eV. The short autodetachment lifetime ofC6H6hyphen;*, however, indicates that (EA)Bis small. Benzene was also studied in mixtures with C2H4and C2H4sngbnd;N2. The results of these latter experiments strongly indicated that the probability of electron detachment inC6H6hyphen;*hyphen;C2H4collisions is large.
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