A simple and efficient scheme based on one-dimensional nanometric thin cell filled with Rb and strong permanent ring magnets allowed direct observation of hyperfine Paschen-Back regime on D 1 line in 0.5 − 0.7 T magnetic field. Experimental results are perfectly consistent with the theory. In particular, with σ + laser excitation, the slopes of B-field dependence of frequency shift for all the 10 individual transitions of 85,87 Rb are the same and equal to 18.6 MHz/mT. Possible applications for magnetometry with submicron spatial resolution and tunable atomic frequency references are discussed. c 2018 Optical Society of America OCIS codes: 020.1335, 300.6360Rubidium atoms are widely used in atomic cooling, information storage, spectroscopy, magnetometry etc [1,2]. Miniaturization of alkali vapor cells is important for many applications [3][4][5][6]. Atom located in magnetic field undergoes shift of the energy levels and change in transition probabilities, therefore precise knowledge of the behavior of atomic transitions is very important [7]. In case of alkali atomic vapor use a sub-Doppler resolution is needed to study separately each individual atomic transition between hyperfine (hf) Zeeman sub-levels of the ground and excited states (in case of a natural mixture of 85 Rb and 87 Rb the number of closely spaced atomic transitions can reach several tens). Recently it was shown that a one-dimensional nanometric-thin cell (NTC) with the thickness of Rb atomic vapor column L = λ, where λ = 794 nm is the wavelength of laser radiation resonant with D 1 line of Rb, is a good tool to obtain subDoppler spectral resolution. Spectrally narrow velocity- When NTC is placed in a weak magnetic field, the VSOPs are split into several components depending on total angular momentum quantum numbers F = I + J, with amplitudes and frequency positions depending on B-field, which makes it convenient to study separately each individual atomic transition.In this Letter we describe a simple and robust system based on NTC and permanent magnets, which allows of achieving magnetic field up to 0.7 T sufficient to observe a hyperfine Paschen-Back regime [9]. The magnetic field required to decouple the nuclear and electronic spins is given by B ≫ A hf s /µ B ∼ = 0.2 T for 87 Rb, and
A time series spatial grid of sea surface temperature (SST) data provided by the archives of Meteo-France and covering the period 1972-1993 was analysed in order to define both the long-term and periodic (mainly seasonal) components at different locations in the Bay of Biscay. The study confirmed the existence of a long-term increasing trend in the SST, but showed that this trend was not homogeneous over the entire area. It revealed also that the amplitude of the cyclic components (summer-winter differences) is spatially heterogeneous. The southeastern part of the Bay of Biscay, close to the French-Spanish border, shows the stronger warming trend (a mean increase of 1.4 "C for the period 1972-1993). This trend decreases in the adjacent regions and is not statistically significant in the northern part of the bay and the Celtic Sea. The increasing trend was recorded both in winter and summer periods with the winter slopes being slightly higher. The amplitude of the SST seasonal changes (summer-winter differences) is stronger close to the southern French Atlantic coast in the area off the Gironde estuary. The lowest values were observed in the SW of the bay in the region of intense upwelling processes. Finally, the analysis of the main components of this series provides a simple empirical model describing the time-related changes in the SST. This model could be useful for studies in the field of biological oceanography and in the context of comparative studies. The possible linkage of these observations with changes in the structure of ecosystem in this area is also discussed. 0 Elsevier, Paris Bay of Biscay / sea surface temperature / time series / long-term trend / seasonal changes Resume-Tendances temporelles et structures spatiales de la temperature de surface de la mer dans le golfe de Gascogne. Une serie chronologique de temperatures de surface de la mer (SST) a eti: analysee pour estimer les tendances a long terme et les composantes ptriodiques (principalement saisonnikes) en differents points d'une grille, dans le golfe de Gascogne. Les donnees, couvrant la periode 1972-1993, sont des valeurs decadaires moyennes fournies par Meteo-France. Le rechauffement a long terme est con&me, avec une reparition heterogene, observee Cgalement pour l'amplitude de la composante periodique (difference CtBhiver). Dans le sud-est du golfe, vers la front&e franco-espagnole, le rechauffement est plus Cleve (en moyenne 1,4 "C de 1972 a 1993). La tendance s'attenue dans les secteurs voisins et devient negligeable dans le nord du golfe et dans la mer Celtique. Le rechauffement, enregistre aussi bien en hiver qu'en CtC, est un peu plus marque en hiver. L'amplitude des variations saisonniitres de la temperature de surface est plus prononcee pres de la c&e dans le secteur influence par l'estuaire de la Gironde. Les plus faibles differences entre l'Ct6 et l'hiver sont observees dans le sud-ouest du golfe, oti les phenomenes d'upwelling sont intenses. L'analyse principales composantes du signal SST fournit un modele empirique simple de...
Simple and efficient "λ-method" and "λ/2-method" (λ is the resonant wavelength of laser radiation) based on nanometric-thickness cell filled with rubidium are implemented to study the splitting of hyperfine transitions of 85 Rb and 87 Rb D1 line in an external magnetic field in the range of B = 0.5 − 0.7 T. It is experimentally demonstrated from 20 (12) Zeeman transitions allowed at low B-field in 85 Rb ( 87 Rb) spectra in the case of σ + polarized laser radiation, only 6 (4) remain at B > 0.5 T, caused by decoupling of the total electronic momentum J and the nuclear spin momentum I (hyperfine Paschen-Back regime). The expressions derived in the frame of completely uncoupled basis (J, mJ ; I, mI ) describe very well the experimental results for 85 Rb transitions at B > 0.6 T (that is a manifestation of hyperfine Paschen-Back regime). A remarkable result is that the calculations based on the eigenstates of coupled (F, mF ) basis, which adequately describe the system for low magnetic field, also predict reduction of number of transition components from 20 to 6 for 85 Rb, and from 12 to 4 for 87 Rb spectrum at B > 0.5 T. Also, the Zeeman transitions frequency shift, frequency interval between the components and their slope versus B are in agreement with the experiment.
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