Hyperfine Paschen–Back regime of potassium D₂ line observed by Doppler-free spectroscopy

Abstract

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 σ + the other one by σ − 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 π-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.

Features of Magnetically-induced atomic transitions of Rb D$_1$ line studied by Doppler-free method based on the second derivative of the absorption spectra

“…The interaction of the vapour with the magnetic field and the optical field is thus treated separately. This simple procedure is in general enough to calculate weak-probe absorption or reflection spectra from NC as was shown by many articles [25,26,27,28].…”

Sub-Doppler spectra of sodium $D$ lines in a wide range of magnetic field: theoretical study

“…One of the possible ways to obtain sub-Doppler resolution during experiments is to use a nano or micrometric thin-cell filled with an atomic vapor. Such experiments have been thoroughly described in [15,16,[35][36][37]. In what follows, we recall briefly the theoretical model that can be used to compute the fields that are reflected S r and transmitted S t through a thin cavity (maximum a few wavelengths) seen as a Fabry-Perot interferometer.…”

Модифицированный Метод Фарадеевского Вращения Для Исследования Атомных Линий Рубидия И Калия В Сверхтонких Ячейках

“…Особо отметим переход под номером 8 в кружке. Это так называемый " направляющий" атомный переход ( " guiding"transition, GT) при использовании излучения с круговой поляризацией σ + (один такой GT-переход есть и при использовании излучения с поляризяцией σ − ) [26]. GT-переходы имеют наибольшую величину вероятности в своей группе, к которой стремятся вероятности всех атомных переходов в его группе в сильных магнитных полях.…”

“…Величина частотного наклона GT-перехода (определяет частотный сдвиг перехода в зависимости от B) составляет s = +1.4 MHz/G. В сильных магнитных полях к этой величине стремятся частотные наклоны всех атомных переходов в его группе [26,27]. Как видно по рис.…”