Attosecond time–energy structure of X-ray free-electron laser pulses

Abstract

Experimental set-up-angular streaking spectroscopy. Previous streaking measurements of XFEL pulses 37-39 used a linearly polarized streaking field to encode their temporal profile onto the kinetic energy of photoelectrons. Depending on the amplitude and phase of

Tunable isolated attosecond X-ray pulses with gigawatt peak power from a free-electron laser

“…For example, the X-ray bandwidth of LCLS can support pulses shorter than 1 fs for hard X-ray energies (40,41). However, the shortest possible pulse duration increases to 1-2 fs for photon energies below 1 keV (42,43), where the relevant core-level absorption edges for light elements are found: carbon (280 eV), nitrogen (410 eV), and oxygen (540 eV). In this letter, we report the generation and time-resolved measurement of gigawatt-scale isolated attosecond soft X-ray pulses with an XFEL.…”

Attoclock Ptychography

“…In a recent experiment, electrons with a mean kinetic energy of approximately 310 eV were analyzed with electron spectrometers with an energy resolution of less than 1 eV [9]. That is, the relative energy resolution was in the order of ≤0.3%.…”

“…However, 10 spectra and more yielded very good results (see, for example, the right inset). Consequently, recent experiments, which were conducted with 16 electron spectrometers arranged on a circle around the interaction volume [9], should have produced sufficient information for high quality reconstruction of complex SASE X-ray waveforms. …”

“…Given the fluctuations that are typical of the electron acceleration as well as the stochastic nature of the self-amplification of spontaneous emission (SASE) nature of such sources, single shot measurement, not scanning, must be used for pulse characterization; no two pulses look alike at an FEL. In this manuscript, therefore, we propose a combination of so-called angular streaking [8,9] with time-domain ptychography for the reconstruction of individual SASE X-ray pulses on a shot-to-shot basis.…”

Electrons or ions? That is the (quantum) question!

“…The speed and precision of electrons ‘jumping’ back and forth are exploited by atomic clocks, with 1 s officially defined as the time it takes for the outer electrons of a caesium‐133 atom to resonate between two energy states a staggering (and ultimately precise) 9,192,631,770 times! Electron transfer can now be ‘clocked’ at the attosecond level (10 −18 or a billionth of a billionth of a second) using ultrashort X‐ray free‐electron laser pulses (Hartmann et al., ), which is incredible resolution considering that there are half as many seconds in the age of the universe as there are attoseconds in 1 s! Such agility [based on pure (Heisenberg) uncertainty] is precisely why it has been suggested that (π)‐electron tunnelling through energetically forbidden regions is likely to form the basis of neuronal (electrochemical potentials firing electrons as electromagnetic waves) and mitochondrial redox signalling (Bailey, ).…”