PEEM image of a group of NTs on excited by femtosecondlaser radiation with photon energy. Insert: TEM image of a NT.
(a) Energy dispersive x-ray spectrum of an area of about on a NT. (b) Intensity line scan of the and signals in (a) along the line denoted in the insert to Fig. 1.
Local spectra of selected NTs [(a) and (b) corresponding to regions A and B in Fig. 1] and the substrate [(c), region C in Fig. 1]. Spectrum (b) after background correction is shown in (d). The probability for direct transitions (e) at the excitation with photons was derived from the calculated DOS.
(a) Calculated DOS of a slab. The arrows denote one possible two-photon transition. denotes the experimental work function. The shaded areas assign the ranges that are energetically allowed to take part in the two-photon excitation. (b) Shows the DOS parts relevant for direct photoexcitation on a shifted energy scale and (c) and (d) are the corresponding probabilities.
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