Precise measurement of h/mn

In a precise measurement of the velocity of neutrons with a well-defined wavelength, the ratio h/mn (h Planck constant, mn neutron mass) was determined to be h/mn=(3.956 034 4±0.000 001 6)x10-7 m2 s-1. It is expected that the uncertainty can be further reduced. A directly measured value of h/mn also improves knowledge of other fundamental physical constants. From the value given above, it follows that, for example, the inverse of the fine-structure constant is α-1=137.035 993±0.000 027. (orig.)