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تسجيل مستخدم جديدHyperfine Paschen-Back regime of Potassium D$_2$ line observed by Doppler-free spectroscopy
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Selective reflection of a laser radiation from an interface formed by a dielectric window and a potassium atomic vapour confined in a nano-cell with $350~$nm gap thickness is implemented for the first time to study the atomic transitions of K D$_2$ line in external magnetic fields. In moderate $B$-fields, there are 44 individual Zeeman transitions which reduce to two groups (one formed by $sigma^+$ the other one by $sigma^-$ circularly-polarised light), each containing eight atomic transitions, as the magnetic field increases. Each of these groups contains one so-called guiding transition whose particularities are to have a probability (intensity) as well as a frequency shift slope (in MHz/G) that are constant in the whole range of $0 - 10~$kG magnetic fields. In the case of $pi$-polarised laser radiation, among eight transitions two are forbidden at $B = 0$, yet their probabilities undergo a giant modification under the influence of a magnetic field. We demonstrate that for $B$-fields $> 165~$G a complete hyperfine Paschen-Back regime is observed. Other peculiarities of K D$_2$ line behaviour in magnetic field are also presented. We show a very good agreement between theoretical calculations and experiments. The recording of the hyperfine Paschen-Back regime of K D$_2$ line with high spectral resolution is demonstrated for the first time.
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A one-dimensional nano-metric-thin cell (NC) filled with potassium metal has been built and used to study optical atomic transitions in external magnetic fields. These studies benefit from the remarkable features of the NC allowing one to use $lambda
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