The energy dependence of superelastic scattering is measured for electrons on Mg(3~1P)from threshold to 270 meV with a novel technique.The method uses photoelectrons produced by a narrow bandwidth laser as an approximately monoenergetic incident electron source to collide with excited atoms.Measurements are made at energies as low as 1.5 meV with a resolution of 1 meV near threshold.An efficient magnetic-bottle time-of-flight electron spectrometer allows for the simultaneous measurement of multiple scattering channels.Above-threshold ionization is also observed.The measured energy dependence for transitions from the 3~1P state to both the 3~3P and 3~1S are found to be inversely proportional to the energy from 10 to 270 meV.Below 10 meV,the dependencies are different,with the 3~3P transition having an E~(-1/2)dependence and the 3~1S channel retaining an E~(-1)dependence.
展开▼
