Fig. 5: Time-resolved photoelectron spectroscopy in the tungsten valence band.

a XUV spectrum generated in an argon gas target (black line) and XUV mirror reflectivity curve (blue filled area) with a maximum reflectivity of 19% and a bandwidth of 4 eV. For better comparability with b and c, their energy plot range is shifted by 6 eV to account for work function and binding energy. The displayed XUV spectrum was measured before the XUV mirror and multiplied with its reflectivity curve. b Static photoelectron spectrum featuring several high-harmonic photoelectron peaks without background subtraction. The peaks can be attributed to sp- and d-bands as indicated by the filled areas (compare Fig. 3a). It is noteworthy that these areas also contain a large amount of secondary electrons (dashed line), which do not contribute to the sideband signal. c RABBITT spectrogram featuring two well-separated oscillating sidebands emitted from the sp- (black dashed line) and d-band (orange dashed line), respectively. For better visibility, a delay-independent background was subtracted (see “Methods”). d Linecuts through the sidebands marked in the same colors in c and the corresponding sine fits. The d-dominated sideband (orange) is delayed by 39 ± 18 asec with respect to the sp-band-dominated sideband (black). The error represents the SD over all traces in the dataset (see “Methods”).