Observation of frequency shifts of spectral lines due to source correlations

Abstract

Wolf has recently shown that the spectrum of radiation from an extended source changes on propagation unless a certain scaling condition is obeyed by the degree of spectral coherence across the source. For a large class of source-coherence functions, the change may be such as to produce red shifts or blue shifts of spectral lines. We have performed an acoustic experiment with two small partially correlated sources and demonstrated Wolf's prediction of frequency shifts of spectral lines by this mechanism.