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Two-dimensional band dispersion and momentum-resolved lifetime of the image-potential state on graphite studied by angle-resolved multiphoton photoemission spectroscopy

2012; American Physical Society; Volume: 85; Issue: 7 Linguagem: Inglês

10.1103/physrevb.85.075325

1550-235X

Kazutoshi Takahashi, Junpei Azuma, Masao Kamada,

Electron and X-Ray Spectroscopy Techniques

We studied the image-potential state (IPS) on a highly oriented pyrolitic graphite surface by means of angle-resolved multiphoton photoemission spectroscopy. The free-electron--like dispersion of IPSs with $n$ = 1, 2, and 3 is observed for the first time with high energy and momentum resolution. From the dependence of the spectral intensity on the excitation density and comparisons with the energy diagram, it is suggested that IPSs are populated by the ${k}_{/\phantom{\rule{-0.16em}{0ex}}/}$-conserved transition from the \ensuremath{\sigma}-band and the indirect transition from the \ensuremath{\pi}-band. The linear dependence of the intrinsic line width on the energy suggests a contribution of intraband relaxation within the IPS band.