Parametric down conversion of X-ray photons

Abstract

Parametric down conversion of X-ray photons in diamond crystals was detected in two experiments, both using the phase-matching scheme ®rst employed in the X-ray regime by Eisenberger & McCall [Phys. Rev. Lett. (1971), 26, 684±688]. The conversion events were detected by a combination of timecorrelation spectroscopy and energy discrimination, using Si drift-chamber detectors. The timecorrelation spectra give a direct comparison of the conversion rate over the accidental coincidence rate. Mechanisms for possible detection of false events and ways to cross check against them are discussed in detail.

Multidimensional Attosecond Resonant X-Ray Spectroscopy of Molecules: Lessons from the Optical Regime

“…Nonlinear effects in the X-ray regime have long been observed in the frequency domain (28), including parametric downconversion (31-33), hard X-ray frequency doubling (34), and two-photon X-ray fluorescence (35). X-ray parametric downconversion has been used to visualize valence charge motion in optically excited diamond crystals (36).…”

X-Ray Second Harmonic Generation

“…It is well known that if the interacting photon energies are all above the electron binding energies, as in the case of the x rays, the magnitudes of nonlinearities are very small. Consequently, previous to the work reported here, hard x-ray nonlinearities have only been observed in parametric down-conversion [2][3][4][5][6][7][8][9]. The key factor for those experiments is the large number of vacuum fluctuation modes at x-ray wavelengths.…”

Nuclear γ-ray superradiance

“…In [2] it was proposed to use parametric down conversion (PDC) to ensure a single-photon event, as well as to obtain a 'start' signal from the photon in the down-converted pair that does not go to the sample. PDC of X-rays is a very weak process [39,40], so it is probably not feasible to use it for the present purpose. However, there are also other ways of achieving the conditional excitation, such as by γ e γ i making use of the time structure of a synchrotron.…”