TOWARDS INTERFEROMETRIC FOURIER SPECTROSCOPY

Most neutron interferometric experiments carried out up till now have dealt with fundamental physics applications. But it was known from the beginning that the interferometric method can open new horizons for s olid state physics research as well. Samples with density or magnetic fluctuations cause inhomogeneous phase shifts which cause a measurable loss of contrast of the interference pattern. Phase topography can be realized without absorbing or scattering neutrons at the object. Very small energy changes (down to 10(-17) eV) become measurable by means of the magnetic neutron Josephson effect. By measuring the neutron coh erence function, one gets direct access to the correlation function G( r, t) instead of measuring its Fourier transform S(Q, omega). Various examples of related investigations are discussed together with their f uture perspectives. The essentials of future neutron Fourier spectrosc opy are formulated.