Tracking Autoionizing-Wave-Packet Dynamics at the 1-fs Temporal Scale

We present time-resolved studies and Fourier transform spectroscopy of inner-shell excited states undergoing Auger decay and doubly excited autoionizing states, utilizing coherent extreme-ultraviolet (XUV) radiation continua. Series of states spanning a range of $\sim 4\mathrm{eV}$ are excited simultaneously. An XUV probe pulse tracks the oscillatory and decaying evolution of the formed wave packet. The Fourier transform of the measured trace reproduces the spectrum of the series. The present work paves the way for ultrabroadband XUV spectroscopy and studies of ultrafast dynamics in all states of matter.

Figure 1

Single-photon ionization scheme of Xe induced by a coherent broadband XUV radiation continuum.

Figure 2

(a) Experimental apparatus. IPG, interferometric polarization gating device; L, lens; GJ1, pulsed Xe gas jet; Si, silicon plate; F, Sn filter; GJ2, pulsed gas jet; TOF, time-of-flight spectrometer; SM, split mirror. (b) Spectrum of the coherent continuum XUV radiation. The black solid and dashed lines in (b) show the spectral position of the autoionizing states within the XUV radiation spectrum.

Figure 3

Ultrafast autoionization dynamics measurement. (a) The trace shown by the grey dashed line is the autoionization signal as a function of the delay between the two XUV pulses, in a coarse scan. A higher-order autocorrelation trace of the fundamental laser field has been used for the calibration of the zero delay value ($\Delta \tau =0\pm 3\mathrm{fs}$) of the trace. (b) Frequency spectrum obtained from the Fourier transform of the raw data of the trace shown in (a). The numbering of the peaks refers to the autoionization states in Table . (c) Traces as in (a) in a fine scan. (d) Frequency spectrum obtained from the Fourier transform of the raw data of the trace shown in (c).

Figure 4

Comparison of the calculated [blue (dark grey) line] and measured (thin grey line) fringe contrast of the autoionization signal. The thin grey line depicts the fringe contrast of the raw data of the recorded trace in Fig. 3a. The moving average of the fringe contrast of the raw data is shown as a red (light grey) line. The green dashed line is an exponential decay fit on the raw data.