We present the first measurement for helium atoms of the tune-out wavelength at which the atomic polarizability vanishes. We utilize a novel, highly sensitive technique for precisely measuring the effect of variations in the trapping potential of confined metastable (23S1) helium atoms illuminated by a perturbing laser light field. The measured tune-out wavelength of 413.0938(9stat)(20syst) nm compares well with the value predicted by a theoretical calculation [413.02(9) nm] which is sensitive to finite nuclear mass, relativistic, and quantum electrodynamic effects. This provides motivation for more detailed theoretical investigations to test quantum electrodynamics.
Henson, B. M., Khakimov, R. I., Dall, R. G., Baldwin, K. G. H., Tang, L. Y., & Truscott, A. G. (2015). Precision Measurement for Metastable Helium Atoms of the 413 nm Tune-Out Wavelength at Which the Atomic Polarizability Vanishes. Physical Review Letters, 115(4), 1-5. . https://doi.org/10.1103/PhysRevLett.115.043004