A method for the quantitative study of atomic transitions in a magnetic   field based on an atomic vapor cell with L=lambda
  We describe the so-called "Lambda-Zeeman method" to investigate individual hyperfine transitions between Zeeman sublevels of atoms in an external magnetic field of 0.1 mT - 0.25 T. Atoms are confined in a nanocell with thickness L = Lambda, where Lambda is the resonant wavelength (794 nm or 780 nm for D1 or D2 line of Rb). Narrow resonances in the transmission spectrum of the nanocell are split into several components in a magnetic field; their frequency positions and probabilities depend on the B-field. Possible applications are described, such as magnetometers with nanometric spatial resolution and tunable atomic frequency references. 
Armen Sargsyan, Grant Hakhumyan, Aram Papoyan, David Sarkisyan, Aigars   Atvars, and Marcis Auzinsh