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Silicon lattice spacing

Silicon lattice spacing

Absolute measurement of lattice spacing of silicon crystals is important for the establishment of a precision wavelength scale for X-ray, gamma-ray and neutron spectroscopies, and also for the determination of fundamental physical constants such as the Avogadro constant and the atomic mass unit.
The lattice spacing d220 of a silicon crystal has been measured with a new combined X-ray and optical interferometer, with relative uncertainty of 0.05 ppm.
@A new optical interferometer (Fig.1) has been installed to measure thedisplacement of the x-ray interferometer. The interferometer is a typeof double-pass Michelson interferometer. It can measure displacement of object over frequency range 0 to 160Hz. The fluctuation of the output signal is less than 3pm for frequency higher than 0.1Hz.

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