Spectral narrowing of x-ray pulses for precision spectroscopy with nuclear resonances

Abstract

Spectroscopy of nuclear resonances offers a wide range of applications due to the remarkable energy resolution afforded by their narrow linewidths. However, progress toward higher resolution is inhibited at modern x-ray sources because they deliver only a tiny fraction of the photons on resonance, with the remainder contributing to an off-resonant background. We devised an experimental setup that uses the fast mechanical motion of a resonant target to manipulate the spectrum of a given x-ray pulse and to redistribute off-resonant spectral intensity onto the resonance. As a consequence, the resonant pulse brilliance is increased while the off-resonant background is reduced. Because our method is compatible with existing and upcoming pulsed x-ray sources, we anticipate that this approach will find applications that require ultranarrow x-ray resonances.

Probing Quantum Dynamical Couple Correlations with Time-Domain Interferometry

“…which is the quantum correspondent of the result found in [5]. Note that the phase difference in this case is given by the Doppler-shift factor Ωt and that an additional phase shift φ must be added to it if the phase control technique developed in reference [14] is used.…”

“…In our scheme, a phase shifter φ controls the interference of these two contributions in the measured intensity of the scattered light, and thus enables one to recover the quantum dynamical couple correlation function of the target. (b) If the split and overlap units are realized using Mössbauer filter foils, then the required phase control is possible using mechanical displacements of the split foil as demonstrated in [14]. (c) A generic implementation of the phase control is a split-and-delay line, with a phase plate in one of the two arms.…”

“…As we will show below, this enables control of the interference between the different scattering channels, and thereby provides access to the full ISF. For Mössbauer foils, the required phase control is possible with sub-Ångstrom precision on a nanosecond scale using mechanical displacements of the split foil, as demonstrated in [14] (see Fig. 1 (b)).…”

Spectral Control of an X-Ray L -Edge Transition via a Thin-Film Cavity

“…The very large bandwidth has drawbacks as well as advantages. On the one hand, many possible interesting experiments involving temporal control and manipulation, such as the creation of x-ray frequency combs [24] and spectral profile manipulation [25], cannot be performed with these electronic x-ray transitions, since they require temporal control not available at the corresponding short timescales. On the other hand, the large bandwidth means that the brilliance of current x-ray sources may permit multiphoton and nonlinear experiments in the near future.…”

Ultimate capabilities for compression of the waveform of a recoilless γ-ray photon into a pulse sequence in an optically deep vibrating resonant absorber

“…Earlier experimental achievements in this field include demonstrations of the Autler-Townes effect [1], γ-ray echo via abrupt shift of a nuclear absorber [2], controllable storage and release of nuclear excitation by switch of the magnetic field direction [3], electromagnetically induced transparency (EIT) via a nuclear level anti-crossing [4], slowing down of γ-photon in a nuclear absorber with a split line [5] and other effects discussed in the review [6]. Recent experimental advances include demonstration of parametric down-conversion in the Langevin regime [7], cav-ity electromagnetically induced transparency [8], collective Lamb shift [9], vacuum-assisted generation of atomic coherences [10], single-photon revival in nuclear absorbing sandwiches [11], phase-sensitive measurements characterizing the quantum state of a nuclei at hard x-ray energies [12], and group velocity control for 14.4 keV-energy photons [13], spectral enhancement of x-ray radiation via a moving absorber [14] and demonstration of a strong coupling between two nuclear polariton modes [15]. Also, a number of important effects were theoretically predicted recently including dynamical control of x-ray polarization qubits by nuclear Mössbauer resonance [16], heralded entanglement between two crystal-hosted macroscopic nuclear ensembles [17], as well as mapping and storing x-ray pulses in a thin-film planar x-ray cavity with embedded resonant nuclear medium [18].…”