A method and apparatus for interrogating a sample that exhibits molecular rotation are disclosed. In practicing the method, the sample is placed in a container having both magnetic and electromagnetic shielding, and Gaussian noise is injected into the sample. An electromagnetic time-domain signal composed of sample source radiation superimposed on the injected Guassian noise is detected, and this signal is cross-correlated with a second time-domain signal produced by the same or similar sample, to produce a cross-correlated signal with frequency domain components. The latter is plotted in the frequency domain by a fast Fourier transform to produce a frequency domain spectrum in a frequency range within DC to 50 KHz. From this spectrum, one or more low-frequency signal components that are characteristic of the sample being interrogated are identified.