Method for quantitative study of atomic transitions in magnetic field based on vapor nanocell with L = λ

Full text: It is well known that atoms placed in an external magnetic field undergo shift of their energy levels and change in their transition probabilities. To study these changes, widely used saturation absorption technique has been used. However, the complexity of Zeeman spectra in magnetic field arises primarily from the presence of strong crossover resonances, which are also split into many components strictly limiting the range of study to 5 -: 50 G, while the most significant changes are expected for B ∼ 1000 G. A method, which we call 'L = λ Zeeman technique' (λ-ZT) has been implemented for investigation of the individual transition between the Zeeman sublevels of the hf structure of alkali atoms in magnetic field 1 -: 2500 G. The λ-ZT is based on the employment of a nanocell with the thickness of Rb vapor column equal to the wavelength of diode laser radiation resonant with D2 line of atomic 85Rb, 87Rb (λ = 780 nm). At the laser intensity 1 mW/cm2, narrow (∼ 10 MHz) resonant velocity selective optical pumping/saturation (VSOP) peaks of reduced absorption appear in the transmission spectrum localized exactly at the atomic transitions. These VSOP peaks are split to separate components in the magnetic field; the amplitudes (which are proportional to transition probability) and frequency positions of the components depend on the B - field. Particularly, it is revealed that in relatively weak magnetic field (∼ 100 G) with σ+- polarized laser radiation also those atomic transitions are recorded, for which new selection rules with respect to the quantum number F take place: 87Rb D2, Fg=1, mF= 1 Fe=3, mF=0 transition (let call it (2)) increases with the increase of the magnetic field, and at B ∼ 200 G becomes equal to probability of the strongest transition Fg=1, mF=+1 Fe=2, mF=+2 (let call it (1)) for B = 0. At higher magnetic field up to 2000 G probability of the atomic transition (2) is the largest, while for B > 2000 G again the probability of (1) is larger than that of (2). Note that implementation of λ-ZT technique is very convenient to study atomic transitions behavior also at higher magnetic field > 2000 G. Particularly, by measuring the frequency difference between transition (1) and transition (2) it is possible to measure a strongly non-homogeneous magnetic field of 150 G/mm. This is achieved by displacement of the nanocell by 10 - 20 μm in the direction of the magnetic field gradient. The theoretical model very well describes the experimental results. Also, the performed studies showed that the atomic transition Fg=1 → Fe=2 of 87Rb D1 line (λ = 794 nm) is very convenient for determination of uniform, as well as strongly non-uniform magnetic field strength in the range of 5 -: 10 000 G. (author)