Department of Physics, Chemistry, and Biology, Linköping University, SE-581 83 Linköping, Sweden. janhe@ifm.liu.se|Department of Physics, Chemistry, and Biology, Linköping University, SE-581 83 Linköping, Sweden. janhe@ifm.liu.se|Department of Physics, Chemistry, and Biology, Linköping University, SE-581 83 Linköping, Sweden. janhe@ifm.liu.se