Bragg atomic spectroscopy

The still necessary increase in accuracy requires an additional effort. A simultaneous spectroscopy of pionic and muonic hydrogen atoms is planned as the muonic X-rays do not show any strong interaction broadening, but exhibit Doppler broadening similar to pionic atoms. A method was found to measure pionic and muonic X-rays simultaneously. The reduced masses of pionic and muonic hydrogen exhibit almost the same ratio as two lattice plane differences of quartz. With a two crystal set up the pionic and muonic X-rays can be Bragg reflected to the same CCD detector. 

Abstract Using our Bose-Einstein condensation (BEC) machine and the Bragg spectroscopy technique we study excitation evolution and decay in BEC. New results have been achieved with this system, and are reported here. We also develop various theoretical models for simulating atomic optical behavior in dynamically changing trapping schemes. 

In order to study the decoherence of quasi-particles within BEC, we use Bragg spectroscopy and Monte Carlo hydrodynamic simulations of the system [Castin 1996], and confirm recent theoretical predictions of the identical particle collision cross-section within a Bose-Einstein condensate. We use computerized tomography [Ozeri 2002] of the experimental images in determining the exact distributions. We then conduct both quantum mechanical and hydrodynamic simulation of the expansion dynamics, to model the distribution of the atoms, and compare theory and experiment [Katz 2002] (see Fig. 2). 

To determine such a modulus, the measurement of the deformation is not made at the macroscopic level but rather at the molecular one using Raman spectroscopy and/or X-ray diffractometry. These experimental methods give access to the absolute modulus from the modifications induced by the applied stress in the Bragg refiection-—and therefore in the position of atoms—, one can indeed evaluate Young s modulus in the direction of stress—and even in the perpendicular direction—thanks to the Hooke law. The values of moduli obtained in this manner are remarkably high. Diamond, which is exclusively constituted of carbon-carbon bonds, has a tensile modulus equal to llbOGPa in the [110] direction for a cross-section of 0.049 nm. In comparison, polyethylene chains which also consist of C-C bonds substituted by hydrogen atoms and whose cross-section is 0.180 nm, should exhibit a tensile modulus of about 310 GPa [i.e 1160 (0.049/0.180)]. This value corresponds almost ideally to the absolute modulus of polyethylene fibers determined at the molecular level by X-ray diffractometry. In contrast, the tensile modulus obtained from a macroscopic measurement of the deformation represents... 

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