Precision measurement of theSi29,S33, and

Abstract

The binding energies of 29 Si, 33 S, and 36 Cl have been measured with a relative uncertainty of <0.59 × 10 −6 using a flat-crystal spectrometer. The unique features of these measurements are (1) nearly perfect crystals whose lattice spacing is known in meters, (2) a highly precise angle scale that is derived from first principles, and (3) a γ -ray measurement facility that is coupled to a high-flux reactor with near-core source capability. The binding energy is obtained by measuring all γ -rays in a cascade scheme connecting the capture and ground states. The measurements require the extension of precision flat-crystal diffraction techniques to the 5-to 6-MeV energy region, a significant precision measurement challenge. The binding energies determined from these γ -ray measurements are consistent with recent highly accurate atomic-mass measurements within a relative uncertainty of 4.3 × 10 −7 . The γ -ray measurement uncertainties are the dominant contributors to the uncertainty of this consistency test. The measured γ -ray energies are in agreement with earlier precision γ -ray measurements.

Refractive Index of Silicon atγRay Energies

“…1. The spectrometer is equipped with 2.5 mm thick single crystals of silicon, the lattice spacing of which has been indirectly measured with ∆d/d ≃ 5 × 10 −8 (for details see [6]). The angular acceptance width of the crystals at γ-ray energies is in the order of nanoradian.…”

“…For each energy about 30 pairs of scans were taken and averaged. The temperature, pressure and humidity at the spectrometer were monitored and time variations of the lattice spacing and the refractive index of air were corrected as described in [6]. For background measurements we compared both beams, removing the wedge from the spectrometer.…”

The role of the international prototype of the kilogram after redefinition of the International System of Units

“…An experiment was reported in 2005 that has been interpreted either as the most accurate experimental test to date of the Einstein relation, E = mc 2 [29], or as a consistency check [30] of two different experimental routes to the same energy value. It is interesting to see that the proposed changes to the SI would have no effect on the interpretation of these results, even if they are significantly improved by future measurements.…”

Status and outlook of CHIP-TRAP: The Central Michigan University high precision Penning trap

“…The 36 Cl (t 1/2 = 3.01 × 10 5 yr) neutron separation energy, which can be obtained from a measurement of the 36 Cl − 35 Cl mass difference, is of interest for a direct test of E = mc 2 . The mass measurement can be compared with high-precision spectroscopy measurements of γ-rays emitted by 36 Cl after cold neutron capture on 35 Cl [9]. The γ-ray spectroscopy measurements have been performed to a precision of 1.8 eV [10], which corresponds to ∼5 ×10 −11 in the cyclotron frequency ratio.…”