科研之友
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摘要
We measured differential cross sections for exciting the three lowest electronically excited states in furan, as functions both of electron energy and of scattering angle. Emphasis of the present work is on recording detailed excitation functions, revealing resonances in the excitation process. The cross section for the first triplet state has a shoulder in the first 2 eV above threshold, assigned to the high-energy tails of the shape resonances, followed by two peaks at 6.5 and 8.0 eV, assigned to two 2(pi, pi*(2)) core-excited shape resonances with substantial configuration mixing. The excitation mechanism thus closely follows that of the prototype case of ethene, except that as the number of double bonds doubles, the numbers of both shape and core-excited resonances also double. The cross section for the singlet states around 6 eV (primarily the S-2 B-1(2) state) rises linearly with energy and attains very high values in the forward direction as expected for a dipole-allowed transition, but has a vertical onset at higher scattering angles, possibly due to a threshold core-excited 2(pi, pi*3 (s) over bar) resonance responsible also for dissociative attachment. Elastic cross sections are also presented. Both elastic and inelastic absolute values compare favorably with existing measurements where available, except very near threshold. The results are compared to existing calculations.
- 出版日期2015-1-12
