  Time-resolved photoelectron spectroscopy (trPES) can directly detect
transient electronic structure, thus bringing out its promising potential to
clarify nonequilibrium processes arising in condensed matters. Here we report
the result of core-level (CL) trPES on 1T-TaS2, realized by developing a
high-intensity 60 eV laser obtained by high-order harmonic (HH) generation.
Ta4f CL-trPES offers the transient amplitude of the charge-density-wave (CDW),
via the site-selective and real-time observation of Ta electrons. The present
result indicates an ultrafast photoinduced melting and recovery of CDW
amplitude, followed by a peculiar long-life oscillation (i.e. collective
amplitudon excitation) accompanying the transfer of 0.01 electrons among
adjacent Ta atoms. CL-trPES offers a broad range of opportunities for
investigating the ultrafast atom-specific electron dynamics in photo-related
phenomena of interest.
