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Using remote methods and materials for meteorological observations, climate changes and the area of 36 thermokarst lakes located in the Anadyr lowland in Chukotka over a 65-year period were analyzed. More than 20 lakes were studied by field methods. With an increase in the average annual air temperature by 1.8°C and an increase in the amount of annual precipitation by 135 mm, the total area of the lakes mirror decreased by 24%. Cryogenic processes have had a significant impact on the decrease in the water quantity of lakes. Thermal erosion in drainage channels has led to multiple discharges of water in abnormally warm years. The heaving of permafrost in the coastal zone affected the reduction of the lake catchment area. If the trends of climate change continue, further drainage of large lakes and an increase in the number of small sag pond is expected in the next 25 years.

For the first time, by analyzing the spatial variations and diurnal dynamics of the water regime of the small river of the Anadyr Lowland, the main sources were studied and the dynamics of the river discharge feeding were estimated. In the midstream and downstream reaches of rivers, the stability of the water regime is ensured by thawed waters of seasonal ice; in mountain rivers’ headwaters, by condensation waters. Suprapermafrost water reserves from the thawing of the upper 30-cm layer vary in low-lying tundra within 80–220 mm. The contribution of meltwater from seasonal ice of the active layer to river discharge at the beginning of the warm season is ≥60% of the total discharge. The water regime of tundra rivers during this period is distinguished by daily cycles in which the water level and temperature are in an antiphase. The modulus of the discharge of condensation waters in the river head from the catchment area, composed of detrital ground, in July–August varies within 15–50 L/km2 s. The condensation waters are characterized by daily in-phase fluctuations in the level and temperature of water in brooks with an amplitude of the temperature of the atmospheric and in-ground air of 16°C. Summer atmospheric precipitation determines the discharge regime of tundra rivers with their abundant fallout (30–60 mm) and complete saturation of the active layer with moisture in August–September. In June, atmospheric precipitation up to 14 mm is completely spent for the evaporation and vegetation of plants and does not affect the river discharge.

The present-day models of the hydrological regime of soils and river basins do not include a hypothesis regarding the effect of atmospheric pressure on hydrological processes (baric effect), which is assumed negligible. However, their manifestations are likely, considering the mechanical and hydrophysical properties of shallow peat-bog soils (plasticity and elasticity, high moisture-retention capacity, the ability to swell and shrink) and the important role of undecomposed plant remains. The effect of atmospheric pressure variations on level changes in a suprapermafrost aquifer was detected using field and laboratory experiments in shallow peat and peaty tundra soils in the Anadyr Lowlands, Northeast Russia. One can see this effect in the runoff regime of 1st–4th orders streams. The manifestations of this phenomenon can differ, and in particular, they can be directed oppositely. The changes in the level and storage of suprapermafrost gravitational water could be caused only by synchronous (in phase opposition) changes in capillary water fringe above the groundwater table. To explain the observed phenomena, a conceptual model is developed based on the analysis of the balance of forces and water balance in a system of elastic capillaries. Not being complete and perfect, the model reproduces qualitatively the main observed cases of the response to air pressure changes, proving the effect itself, and suggests the likely localization of its mechanisms. A shallow suprapermafrost groundwater table in contact with the peat bottom, as well as incomplete (below the full moisture capacity) water saturation of peat soil horizons, appear to be circumstances of the baric effect on tundra shallow subsurface aquifers. Favorable conditions for the baric effect in a soil profile include a high elasticity of peat-soil matrix, high and variable values of porosity and water yield of peat and moss cover, and, at the catchment scale, a high proportion of coverage by these types of soils. A full-scale study of a mechanism of baric effect on a suprapermafrost tundra aquifer requires numerous laboratory and field experiments, that must be much better equipped than presented in our study. It is also welcomed alternative hypotheses regarding the aquifer water level response to changes in air pressure if the observed macroscopic effects at any alternative occurrence could be quite similar.

A scheme is proposed for the third stage of laser cooling of thulium atoms at a wavelength of 506.2 nm, and a system for stabilising the laser radiation frequency is described, which provides the required characteristics. The transition at a wavelength of 506.2 nm is detected in a magneto-optical trap with the employment of the developed laser setup. The value of hyperfine splitting of the transition upper level is measured, and the single-dimension cooling at this wavelength is observed for the first time.

A population transfer from the upper level of the clock transition in thulium atoms to the ground level is demonstrated by using radiation with a wavelength of 402 nm. The method for detecting the clock transition excitation that is not affected by technical fluctuations of the number of atoms in an optical lattice is investigated. The hyperfine splitting of the |4f12(3F2)5d5/2 6s2; J = 7/2〉 level in the thulium atom is measured to be 1480(9) MHz. The suggested method for population transfer can be applied to both the hyperfine components of the clock transition intended for compensating Zeeman effect in a thulium optical clock.

The clock transition at a wavelength of 1.14 μm in thulium atoms in an optical lattice in the Lamb – Dick regime is studied. The capture of thulium atoms makes it possible to suppress completely both the transition broadening due to the first-order Doppler effect and the shift of the transition frequency caused by the recoil effect. The excitation spectra of sideband oscillation frequencies and Rabi oscillations of population between the clock transition levels upon resonance excitation are investigated.

Differential dynamic polarisability of the inner-shell clock transition at a wavelength of 1.14 μm in the thulium atom is measured by the method of precision laser spectroscopy in the spectral range of 800 – 860 nm. Experimental data approximated by a theoretical model yield the probability of the transition at λ = 809.5 nm: A809.5 = 460(70) s−1. The values of two magic wavelengths are obtained experimentally, namely, λ m1 = 807.727(18) nm and λ m2 = 813.3(2) nm, the wavelength of λ m1 being determined for the first time. Main parameters of an optical lattice at these wavelengths are compared and a conclusion is made that trapping thulium atoms in an optical lattice at λ m2 is preferable for optical clock operation.

We characterize a 1.14 μm ultrastable semiconductor laser system for precision spectroscopy of Tm inner-shell clock transition using a frequency comb. We stabilize both the repetition and the carrierenvelope offset frequencies of a commercial Ti : sapphire femtosecond laser to a passive hydrogen maser using a home-built f-2f interferometer. By measuring the absolute frequency of the 1.14 μm laser stabilized to a high-finesse ULE cavity, we determine the zero-expansion temperature point of the cavity and the rate of linear drift of the the cavity resonance frequency due to “aging” of the ULE glass. We achieve less than 10 Hz frequency instability of the laser within 1,000 s after the linear drift compensation. We also measured the absolute frequency of the 1.14 μm transition in Tm to be 262 954 938 269 213(30) Hz.

The article presents the results of a study of water supply sources and the daily flow regime of rivers and streams of the Anadyr lowland in the low-water period of 2019. Regarding the field materials, the problem of the impact of atmospheric pressure surges on the water-physical properties of peat soils and the runoff regime of small rivers in the cryolithozone lowlands is considered. It was found that the daily atmospheric pressure drop with an amplitude of 1.2 kPa in the Ugolnaya-Dionisiya River watershead, located within the Anadyr Lowland in Chukotka, led to a synchronous decrease and then an increase in the level of suprapermafrost and river waters by 2.5– 7.8 cm. The water-physical properties of peat soils are described, the mechanism of the influence of atmospheric pressure on the tundra soils moisture capacity and the small rivers runoff during the summer dry season is proposed. The geocryological, hydrogeological and hydrological conditions necessary for the manifestation of discovered effect are considered. The known mechanical properties of the tundra peat cover and the water-physical properties of the organogenic horizon of tundra soils made allow to propose a hypothesis of the effect of atmospheric pressure on the level of suprapermafrost waters by changing the moisture capacity of peat during its plastic-elastic deformation. The condition for a positive reaction of suprapermafrost and river runoff to fluctuations in atmospheric pressure are: the bedding of the groundwater table in contact with the peat horizon; incomplete moisture capacity of the organogenic soil horizon; predominant feeding of the river by suprapermafrost waters and the presence of an extensive drainage network. It seems promising to further study the atmospheric baric effects of baroeffects in the underground and surface waters of the lowlands of the permafrost zone, as well as in the bog landscapes of more southern latitudes, where there are conditions for their manifestation. In the landscape conditions of the Anadyr Lowland, in the absence of atmospheric precipitation, pressure jumps in the level of suprapermafrost waters can be considered as a mechanism for additional moisture replenishment of the root layer of soils during the period of active vegetation of tundra vegetation., В статье представлены результаты исследования источников питания и суточного режима стока рек и ручьев Анадырской низменности в меженный период 2019 года. На примере полевых материалов рассмотрена проблема воздействия скачков атмосферного давления на водно-физические свойства торфяных почв и режим стока малых рек низменностей криолитозоны. Установлено, что суточный перепад атмосферного давления амплитудой 1,2 кПа в районе реки Угольная-Дионисия, расположенной в границах Анадырской низменности на Чукотке, привел к синхронному понижению, а затем повышению уровня надмерзлотных подземных и поверхностных речных вод в бассейне реки на 2,5–7,8 см. Описаны водно-физические свойства торфяных почв, предложен механизм воздействия атмосферного давления на влагоемкость тундровых почв и сток малых рек в фазу летней межени. Рассмотрены геокриологические, гидрогеологические и гидрологические условия необходимые для проявления обнаруженного эффекта воздействия скачков атмосферного давления на речной сток. Известные механические свойства торфяного покрова тундр и водно-физические свойства органогенного горизонта тундровых почв позволили предложить гипотезу воздействия атмосферного давления на уровень надмерзлотных вод посредством изменения влагоемкости торфа при его пластично-упругой деформации. Условием положительной реакции надмерзлотного и речного стока на скачки атмосферного давления являются: контактное с торфяным горизонтом почв залегание зеркала подземных вод; неполная влагоемкость органогенного горизонта почв; преимущественное питание реки надмерзлотными водами и наличие разветвленной дренажной сети. Представляется перспективным дальнейшее изучение атмосферных барических эффектов в подземных и поверхностных водах низменностей криолитозоны, а также в болотных ландшафтах более южных широт, где имеются условия для их проявления. В ландшафтных условиях Анадырской низменности при отсутствии атмосферных осадков барические скачки уровня надмерзлотных вод могут рассматриваться как механизм дополнительной подпитки влагой корнеобитаемого слоя почв в период активной вегетации тундровой растительности. Литература: Амарян Л.С. Свойства слабых грунтов и методы их изучения. М.: Недра, 1990. 219 с. Ермичев В.А., Лобанов В.Н., Кривченкова Г.Н., Артемов А.В. Прогнозирование осадки и плотности лесных почв после проезда гусеничных машин // Известия высших учебных заведений. Лесной журнал. 2006. № 2. С. 48–51. Зырянов В.Н., Хубларян М.Г. Пампинг-эффект в теории нелинейных процессов типа уравнения теплопроводности и его приложение в геофизике // Доклады академии наук. 2006. Т.408. № 4. С. 535–538. Иванов К.Е. Водообмен в болотных ландшафтах. Л.: Гидрометеоиздат, 1975. 280 с. Каменский Г.Н., Биндеман Н.Н., ВевиоровскаяМ.А., Альтовский М.Е. Режим подземных вод. М.-Л.: ГОНТИ, Главная редакция строительной литературы, 1938. 192 с. Лавров С.А., Марков М.Л. Оценка влияния атмосферного давления на уровень и сток грунтовых вод // Инженерные изыскания. 2018. Т.12. №11-12. С.44-51. DOI: 10.25296/1997-8650-2018-12-11-12-44-51. Марунич С.В., Завилейский С.В., Ливанова Н.А. Влияние изменения атмосферного давления на формирование речного стока // Известия Академии наук. Серия географическая. 1998. №1. С.111–115. Соколов Б.Л., Завилейский С.В., Марунич С.В. Экспериментальные исследования процессов формирования речного стока малых водосборов// Метеорология и гидрология. 1994. № 10. С. 82–91. Трегубов О.Д., Гарцман Б.И., Лебедева Л.С., Нутевекет М.А., Тарбеева А.М., УяганскийК.К., Шекман Е.А., Шепелев В.В. Ландшафтно-мерзлотные условия и факторы формирования летнего стока малых рек приморской низменности криолитозоны // Сборник докладов международной научной конференции памяти выдающегося русского ученого Юрия Борисовича Виноградова «Четвертые Виноградовские чтения. Гидрология: от познания к мировоззрению» (г.Санкт-Петербург, 23–31 октября 2020 года). СПб.: Изд-во ВВМ, 2020. С. 805–810. Трегубов О.Д., Гарцман Б.И., Тарбеева А.М., Лебедева Л.С., Шепелев В.В. Пространственная и временная динамика источников питания и водного режима рек Анадырской низменности // Водные ресурсы. 2021. Т. 48. № 4. С. 427–438. DOI: 10.31857/S0321059621040180. Трегубов О.Д., Уяганский К.К., Нутевекет М.А. Мониторинг мерзлотно-климатических условий Анадырской низменности // География и природные ресурсы. 2020. № 2 (161). С. 143–152. DOI: 10.21782/GiPR0206-1619-2020-2(143-152). Фомин Ю.В. Природа пампинг-эффекта в прибрежной зоне // Труды Гидрометеорологического научно-исследовательского центра Российской Федерации. 2016. Вып. 361. С. 203–230. Штенгелов Р.С., Филимонова Е.А., Шубин И.С. Обработка откачки из напорного водоносного горизонта при переменном дебите и атмосферном давлении // Вестник Московского университета. Серия 4: Геология. 2017. № 3. С.50–58. DOI: 10.33623/0579-9406-2017-3-50-58. Hylckama T.E.A.V. Water level fluctuations in evapotranspirometers // Water Resources Research. 1968. Vol. 4. Iss. 4. Рp. 761–768. DOI:10.1029/WR004i004p00761. Lautz L.K. Estimating groundwater evapotranspiration rates using diurnal water-table fluctuations in semi-arid riparian zone // Hydrogeology Journal. 2008. Vol. 16. Iss. 3. Pp.483–497. DOI: 10.1007/s10040-007-0239-0. Moraetis D., Efstathiou D., Stamati F., Tzoraki O., Nikolaidis N.P., Schnoor J.L., Vozinakis K. High-frequency monitoring for the identification of hydrological and bio-geochemical processes in a Mediterranean river basin // Journal of Hydrology. 2010. Vol. 389. Iss. 1-2. Pp. 127–136. DOI:10.1016/j.jhydrol.2010.05.037. Salama R.B., Bartle G.A., Farrington P. Water use of plantation Eucalyptus camaldulensis estimated by groundwater hydrograph separation techniques and heat pulse method // Journal of Hydrology. 1994. Vol. 156. Iss. 1–4. Pp. 163–180. DOI:10.1016/0022-1694(94)90076-0. Turk L.J. Diurnal fluctuations of water tables induced by atmospheric pressure changes // Journal of Hydrology. 1975. Vol. 26. Iss. 1–2. Pp. 1–16. DOI: 10.1016/0022-1694(75)90121-3. Zhuravin S.A., Markov M.L. Development of studies in small research basins in Russia and the most recent tasks // Proceedings of the Workshop «Status and Perspectives of Hydrology in Small Basins» (Goslar-Hahnenklee, Germany, 30 March–2 April 2009). IAHS Publ., 2010. No. 336. Р. 219–224 Амарян Л.С. Свойства слабых грунтов и методы их изучения. М.: Недра, 1990. 219 с. Ермичев В.А., Лобанов В.Н., Кривченкова Г.Н., Артемов А.В. Прогнозирование осадки и плотности лесных почв после проезда гусеничных машин // Известия высших учебных заведений. Лесной журнал. 2006. № 2. С. 48–51. Зырянов В.Н., Хубларян М.Г. Пампинг-эффект в теории нелинейных процессов типа уравнения теплопроводности и его приложение в геофизике // Доклады академии наук. 2006. Т.408. № 4. С. 535–538. Иванов К.Е. Водообмен в болотных ландшафтах. Л.: Гидрометеоиздат, 1975. 280 с. Каменский Г.Н., Биндеман Н.Н., ВевиоровскаяМ.А., Альтовский М.Е. Режим подземных вод. М.-Л.: ГОНТИ, Главная редакция строительной литературы, 1938. 192 с. Лавров С.А., Марков М.Л. Оценка влияния атмосферного давления на уровень и сток грунтовых вод // Инженерные изыскания. 2018. Т.12. №11-12. С.44-51. DOI: 10.25296/1997-8650-2018-12-11-12-44-51. Марунич С.В., Завилейский С.В., Ливанова Н.А. Влияние изменения атмосферного давления на формирование речного стока // Известия Академии наук. Серия географическая. 1998. №1. С.111–115. Соколов Б.Л., Завилейский С.В., Марунич С.В. Экспериментальные исследования процессов формирования речного стока малых водосборов// Метеорология и гидрология. 1994. № 10. С. 82–91. Трегубов О.Д., Гарцман Б.И., Лебедева Л.С., Нутевекет М.А., Тарбеева А.М., УяганскийК.К., Шекман Е.А., Шепелев В.В. Ландшафтно-мерзлотные условия и факторы формирования летнего стока малых рек приморской низменности криолитозоны // Сборник докладов международной научной конференции памяти выдающегося русского ученого Юрия Борисовича Виноградова «Четвертые Виноградовские чтения. Гидрология: от познания к мировоззрению» (г.Санкт-Петербург, 23–31 октября 2020 года). СПб.: Изд-во ВВМ, 2020. С. 805–810. Трегубов О.Д., Гарцман Б.И., Тарбеева А.М., Лебедева Л.С., Шепелев В.В. Пространственная и временная динамика источников питания и водного режима рек Анадырской низменности // Водные ресурсы. 2021. Т. 48. № 4. С. 427–438. DOI: 10.31857/S0321059621040180. Трегубов О.Д., Уяганский К.К., Нутевекет М.А. Мониторинг мерзлотно-климатических условий Анадырской низменности // География и природные ресурсы. 2020. № 2 (161). С. 143–152. DOI: 10.21782/GiPR0206-1619-2020-2(143-152). Фомин Ю.В. Природа пампинг-эффекта в прибрежной зоне // Труды Гидрометеорологического научно-исследовательского центра Российской Федерации. 2016. Вып. 361. С. 203–230. Штенгелов Р.С., Филимонова Е.А., Шубин И.С. Обработка откачки из напорного водоносного горизонта при переменном дебите и атмосферном давлении // Вестник Московского университета. Серия 4: Геология. 2017. № 3. С.50–58. DOI: 10.33623/0579-9406-2017-3-50-58. Hylckama T.E.A.V. Water level fluctuations in evapotranspirometers // Water Resources Research. 1968. Vol. 4. Iss. 4. Рp. 761–768. DOI:10.1029/WR004i004p00761. Lautz L.K. Estimating groundwater evapotranspiration rates using diurnal water-table fluctuations in semi-arid riparian zone // Hydrogeology Journal. 2008. Vol. 16. Iss. 3. Pp.483–497. DOI: 10.1007/s10040-007-0239-0. Moraetis D., Efstathiou D., Stamati F., Tzoraki O., Nikolaidis N.P., Schnoor J.L., Vozinakis K. High-frequency monitoring for the identification of hydrological and bio-geochemical processes in a Mediterranean river basin // Journal of Hydrology. 2010. Vol. 389. Iss. 1-2. Pp. 127–136. DOI:10.1016/j.jhydrol.2010.05.037. Salama R.B., Bartle G.A., Farrington P. Water use of plantation Eucalyptus camaldulensis estimated by groundwater hydrograph separation techniques and heat pulse method // Journal of Hydrology. 1994. Vol. 156. Iss. 1–4. Pp. 163–180. DOI:10.1016/0022-1694(94)90076-0. Turk L.J. Diurnal fluctuations of water tables induced by atmospheric pressure changes // Journal of Hydrology. 1975. Vol. 26. Iss. 1–2. Pp. 1–16. DOI: 10.1016/0022-1694(75)90121-3. Zhuravin S.A., Markov M.L. Development of studies in small research basins in Russia and the most recent tasks // Proceedings of the Workshop «Status and Perspectives of Hydrology in Small Basins» (Goslar-Hahnenklee, Germany, 30 March–2 April 2009). IAHS Publ., 2010. No. 336. Р. 219–224.

Optical atomic clocks have already overcome the eighteenth decimal digit of instability and uncertainty, demonstrating incredible control over external perturbations of the clock transition frequency. At the same time, there is an increasing demand for atomic (ionic) transitions and new interrogation and readout protocols providing minimal sensitivity to external fields and possessing practical operational wavelengths. One of the goals is to simplify the clock operation while maintaining the relative uncertainty at a low 10−18 level achieved at the shortest averaging time. This is especially important for transportable and envisioned space-based optical clocks. Here, we demonstrate implementation of a synthetic frequency approach for a thulium optical clock with simultaneous optical interrogation of two clock transitions. Our experiment shows suppression of the quadratic Zeeman shift by at least three orders of magnitude. The effect of the tensor lattice Stark shift in thulium can also be reduced to below 10−18 in fractional frequency units. This makes the thulium optical clock almost free from hard-to-control systematic shifts. The “simultaneous” protocol demonstrates very low sensitivity to the cross-talks between individual clock transitions during interrogation and readout., There are continuous efforts in improving the stability and systematic shifts of optical clocks. Here the authors demonstrate thulium optical clock utilizing bicolor scheme involving interrogation of both hyperfine levels and they are able to cancel the quadratic Zeeman shift.

In this work we discuss interrogation scheme required for the use of synthetic frequency in thulium optical lattice clock and underlying specifics of servo signal generation. In order to achieve insensitivity of the synthetic frequency to periodic oscillations of the magnetic field, simultaneous interrogation of two clock transitions is beneficial, which complicates optimization of digital lock parameters and may result in crosstalk. We used numerical simulations to test the performance of digital locks and verify absence of systematic frequency shifts related to the interrogation scheme.

The 1.14 µm inner-shell magnetic dipole transition in neutral thulium possesses very low blackbody radiation shift in comparison to other neutrals. Together with other features of Tm electronic structure it opens new perspectives for compact optical clocks almost free from hard-to-control systematic shifts.

The series of 20-year-long observations of seasonal thawing have been studied on CALM plots in Eurasia and North America. The short-term (2-5 years) fluctuations of the active layer are considered. Similarities and differences in seasonal thawing of tundra soils in circumpolar countries are noted. The dynamics of seasonal thawing is analyzed by the example of two CALM plots in the Chukotka Autonomous District. Time series of changes in the depth of seasonal thawing are described using the mathematical methods. The amplitude, frequency and periods of oscillations are determined for them. The comparative graphical and statistical analysis of climate and seasonally thawed layer variations allowed us to judge on the nature and degree of influence of meteorological factors on the depth of soil thawing. The problems of interpretation of intra-century fluctuations of climatic parameters and seasonal thawing are considered. It is concluded that the duration of the warm season affects significantly the depth of seasonal thawing. It is noted that ignoring the intra-century variations in the parameters of climatic and permafrost landscapes is the cause of inconsistency of judgments about climate change trends and forecasts of permafrost degradation. A new concept of “climatic year” was proposed as the conjugation of weather conditions for 2-3 years equally affecting the depth of thawing. The established statistical regularities in changing permafrost-climatic conditions can be used for the preparation of 3-5 and 10-15 summer weather forecasts. The use of the ratio of the average values of the amplitude to the period of short oscillations as an indicator of the stability of the roof of permafrost is justified. The hypothesis of the influence of solar and technogenic electromagnetic radiation in the radio-wave range on the degradation of underground ice of the active layer and Arctic ice is proposed.

The atomic energy levels corresponding to states with the zero projection of the total angular momentum have a weak sensitivity to certain sources of shifts and, therefore, are widely used in precision spectroscopy. The optical pumping of ultracold thulium atoms to the ground state level with the zero projection of the total angular momentum is described. The population dynamics of this state due to magnetic dipole − dipole interaction in an external magnetic field is studied.

One of the key systematic effects limiting the performance of state-of-the-art optical clocks is the blackbody radiation (BBR) shift. Here, we demonstrate unusually low sensitivity of a 1.14 μm inner-shell clock transition in neutral Tm atoms to BBR. By direct polarizability measurements, we infer a differential polarizability of the clock levels of −0.063(30) atomic units corresponding to a fractional frequency BBR shift of only 2.3(1.1) × 10−18 at room temperature. This amount is several orders of magnitude smaller than that of the best optical clocks using neutral atoms (Sr, Yb, Hg) and is competitive with that of ion optical clocks (Al+, Lu+). Our results allow the development of lanthanide-based optical clocks with a relative uncertainty at the 10−17 level., Precise and stable optical clocks are important for fundamental science and applications. Here the authors demonstrate a clock transitions in thulium (Tm), which has a small black body radiation frequency shift and is suitable for transportable atomic clocks.

We eliminate the largest systematic shift in thulium optical clock — the second-order Zeeman shift — using average frequency of two clock transitions. This reduces the total systematic shift down to mHz level.

Because of the low sensitivity of a thulium optical clock to black-body radiation and good accuracy and stability estimations, it is considered as a promising transportable optical clock. One of the leading systematic effects for Tm clock transition, i.e., the second-order Zeeman effect, can be canceled by probing two clock transitions between different hyperfine levels of ground and metastable states during clock operation. Herein, we demonstrate efficient optical pumping into the ${m}_{F}=0$ state of both ground hyperfine levels using single-frequency radiation at 418.8 nm. We prepared the atoms in both target states simultaneously and excited two clock transitions alternately. The resulting population of ${m}_{F}=0$ states of ground hyperfine levels was 36% and 3.8% of the initial number of atoms with less than 4% and 0.4% on nonzero magnetic sublevels, respectively. We performed numerical simulations of the optical pumping process, which is able to explain experimental results well.

It is known that atmospheric pressure surges affect the discharge of underground water sources in large artesian basins. In southern latitudes, the groundwater tables change insignificantly following the diurnal variations of atmospheric pressure. There is no information on the influence of rapid changes in atmospheric pressure on the position of the surface of the suprapermafrost waters and river flow in the Arctic region. The study of the diurnal course of the level of underground suprapermafrost and surface waters was carried out to identify the links of river flow with atmospheric phenomena and cryogenic processes. It was found that the daily atmospheric pressure drop with an amplitude of 1.2 kPa in the area of the small Ugolnaya-Dionisia river, located in the Anadyr lowland in Chukotka, led to a simultaneous decrease and then an increase in the level of suprapermafrost underground and surface river basin waters by 2.5-7.8 cm. This corresponds to a short-term decrease and then an increase in the river water discharge by more than 3.5 times. To clarify the factors that determine the mechanism of the influence of atmospheric pressure on the water level and river flow, a consideration of the hydrophysical properties of aquifer-containing peat soils was carried out. Compression tests revealed that the elasticity of the peat soils horizon remains within the range of 0-15 kPa, which contributes to a dynamic change in porosity even with a slight change in the external load. This means that the atmospheric pressure changes during weather development are sufficient to modify the water capacity of peat soils and deposit them, and then discharge a part of the suprapermafrost flow. The discovered pressure impact in the tundra soils of the permafrost zone is a unique mechanism for providing plants with moisture during droughts and reducing the risk of tundra fires. As part of the further study of the pressure impact, it is planned to conduct laboratory experiments to determine the quantitative parameters of the change in the peat soils moisture capacity under pressure drops in the atmosphere. Mathematical modeling of the capillary moisture capacity of peat soils will be performed under conditions of ambient load changes. The results of experiments and theoretical studies are assumed to be useful for predicting the flow of bogged-up river basins, design of reclamation, and irrigation of areas of peat soils distribution.

We calculate uncertainty budget of a developing thulium optical lattice clock. We estimate necessary level of control over various experimental parameters to achieve total systematic uncertainty of better than 10−17 in fractional units. We show, that clock transition frequency is insensitive to an ambient temperature, as well as quadratic Zeeman shift when interrogating two transition between different hyperfine levels. The optical lattice shift of the clock transition frequency is below 1 mHz for the lattice laser frequency stability of better than 3 MHz around the magic wavelength and relative fluctuation of the lattice polarization and a bias magnetic field of less than 1 mrad.

The development of new optical technology plays a key role in the essential evolution of optical science. In this article, we experimentally demonstrate an optical technology that enables the arbitrary manipulation of amplitudes and phases of highly discrete spectra. This optical technology is simple and practically useful: we may only place a few fundamental optical elements on an optical axis and control their thicknesses precisely. As a typical application, we show generation of a train of ultrashort pulses in the time domain, with a pulse duration close to 1 fs and a repetition rate exceeding 100 THz.

We discuss extension of a recently proposed method based on continuous spectroscopy of 88Sr atoms trapped into a moving optical lattice [Appl. Phys. Express,14(7),072006(2021)] to operation of bicolor thulium optical clocks. Simultaneous interrogation of two clock transitions at 1.14μm and building up a synthetic frequency provides a straightforward way to significantly suppress the first-order Doppler shift and cancel out the second-order Zeeman shift, the latter being one of the major uncertainty sources in the originally proposed 88Sr setup. In our configuration, the total systematic frequency shift is 4×10−16 and instability at or lower than 10−18 after 1 hour of integration.

We have developed a compact vacuum system for laser cooling and spectroscopy of neutral thulium atoms. Compactness is achieved by obviating a classical Zeeman slower section and placing an atomic oven close to a magneto-optical trap (MOT), specifically at the distance of 11 cm. In this configuration, we significantly gained in solid angle of an atomic beam, which is affected by MOT laser beams, and reached 1 million atoms loaded directly in the MOT with only 15 mW of MOT cooling beams net power. By exploiting Zeeman-like deceleration of atoms with an additional laser beam and tailoring the MOT magnetic field gradient with a small magnetic coil, we demonstrated trapping of up to 13 million atoms. These results show great perspective of the developed setup for realizing a compact high-performance optical atomic clock based on thulium atoms.

We consider an experiment on trapping and laser cooling of 229Th3+ ions in a linear Paul trap in the presence of undesirable impurities such as ions of the radioactive isotope 228Th3+. We suggest a method of separating these impurities by means of selective laser cooling utilizing the isotope shift of cooling transitions in 229Th3+ and 228Th3+ ions. According to our estimation, the isotope shift is equal to 3.4 GHZ and makes laser separation of these isotopes possible.

We demonstrate a simple and efficient readout procedure of the 1.14^m clock transition excitation efficiency in neutral thulium atoms. Our method utilizes additional but short clock n-pulse to measure number of atoms excited by spectroscopic clock pulse, that allows to determine excitation probability insensitive to fluctuation of number of atoms in the trap. It is important that this method can be used for both hyperfine components of the clock transition and does not require any additional lasers in the setup.

We review the current research on precision spectroscopy and quantum optics applications of laser-cooled lanthanides. We discuss the specific electronic structure of hollow atoms, which determine prospects for application in optical frequency standards and in quantum simulators based on spin interactions in optical lattices. Using the example of the thulium atom, we describe the specifics of laser cooling, optical lattice trapping techniques, and clock transition spectroscopy using spectrally narrow lasers.

The experience gained in using ground-penetrating radar to study the frozen subgrade of foundations in the city of Anadyr in the Chukotka Autonomous Region is analyzed. An algorithm for performing geophysical investigations is presented and a standard, typical, geological-geophysical sectional profile is composed. The identification of newly formed layers of frozen ground (NFG) within the boundaries of populated points is substantiated. The particularities of NFG in brownfield construction zones are examined.

We report on the improved measurement of the hyperfine structure of $4f^{12}(^3 H_6)5d_{5/2}6s^2$ $(J=9/2)$ excited state in Tm-169 which is involved in the second-stage laser cooling of Tm. To measure the absolute value of the hyperfine splitting interval we used Doppler-free frequency modulation saturated absorption spectroscopy of Tm atoms in a vapor cell. The sign of the hyperfine constant was determined independently by spectroscopy of laser cooled Tm atoms. The hyperfine constant of the level equals $A_J=-422.112(32)$ MHz that corresponds to the energy difference between two hyperfine sublevels of $-2110.56(16)$~MHz. In relation to the saturated absorption measurement we quantitatively treat contributions of various mechanisms into the line broadening and shift. We consider power broadening in the case when Zeeman sublevels of atomic levels are taken into account. We also discuss the line broadening due to frequency modulation and relative intensities of transitions in saturated-absorption experiments.

Scalar and tensor polarizabilities of 5D 3/2 and 5D 5/2 levels of rubidium were measured in a cloud of cold atoms. The measurements were carried out by using the shift of spectral lines corresponding to 5P–5D transitions in a constant external electric field. The following values of polarizabilities were obtained: αS(5D 3/2) = 18 400 (75), αT(5D 3/2) = –750 (30), α(5D 5/2) = 18 600 (76), and αT(5D 5/2) = –1440 (60).

We describe an original multisectional quadrupole ion trap aimed to realize nuclear frequency standard based on the unique isomer transition in thorium nucleus. It is shown that the system effectively operates on Th+, Th2+ and Th3+ ions produced by laser ablation of metallic thorium-232 target. Laser intensity used for ablation is about 6 GW/cm2. Via applying a bias potential to every control voltage including the RF one, we are able not only to manipulate ions within the energy range as wide as 1–500 eV but to specially adjust trap potentials in order to work mainly with ions that belong to energy distribution maximum and therefore to effectively enhance the number of trapped ions. Measurement of energy distributions of 232Th+, 232Th2+, 232Th3+ ions obtained by laser ablation allows us to define optimal potential values for trapping process. Observed number of ions inside trap in dependence on trapping time is found to obey an unusually slow – logarithmic decay law that needs more careful study.

Second-stage laser cooling of thulium atoms at the 530.7 nm transition with a natural linewidth of 350 kHz offers an interesting possibility to study different regimes of a magneto-optical trap (MOT). The intermediate value of the spectral linewidth of the cooling transition allows the observation of three distinct regimes depending on intensity and detuning of the cooling beams. Namely, the "bowl-shaped" regime when light pressure force competes with gravity, the "double structure" regime with interplay between Doppler and polarization-gradient (sub-Doppler) cooling, and the "symmetric" regime when Doppler cooling dominates over sub-Doppler cooling and gravity. The polarization-gradient cooling manifests itself by a two-temperature momentum distribution of atoms resulting in a double-structure of the spatial MOT profile consisting of a cold central fraction surrounded by a hot halo. We studied the "double structure" regime at different saturation parameters and compared observations with calculations based on semiclassical and quantum approaches. The quantum treatment adequately reproduces experimental results if the MOT magnetic field is properly taken into account., Comment: 7 pages, 6 figures

We determine a lifetime of the 4/f 136s 2 (J = 5/2) clock level in 169Tm atoms trapped in an optical lattice at 532 nm directly exciting a 1.14 μm magneto-dipole transition and measuring a decay rate from this level to the ground (J = 7/2) state. The measured lifetime of 112(4) ms corresponds to a transition spectral line width of 1.4 Hz which is in a good agreement with a theoretical prediction of 1.14 Hz.

This paper describes the techniques of production and trapping of thorium ions required to perform spectroscopic studies of thorium nuclear transition.

We report on accurate measurements of the scalar and tensor polarizabilities of the 5D fine structure levels 5D3/2 and 5D5/2 in Rb. The measured values show reasonable correspondence to previously published theoretical predictions, but are more accurate. We implemented laser excitation of the 5D level in a laser cooled cloud of optically polarized Rb-87 atoms placed in a constant electric field., 8 pages, 9 figures

A Russian geographer investigates the possibility of using geochemical field parameters in large-scale landscape-geochemical mapping of the Anadyr' Lowland in Chukotka, Russia. Variations in the dispersion of the concentrations of chemical elements in soil samples serve as a mapping criterion that makes it possible to discriminate elementary landscapes that differ in terms of their constituent chemical elements. Translated by Edward Torrey, Alexandria, VA from: Izvestiya Akademii Nauk, seriya geograficheskaya, 1998, No. 4, pp. 116-124.

The authors examine the migration of pollutants in soil and snow meltwaters in far Northeast Siberia with an emphasis on detection and analysis of the secondary concentration of pollutants in icings created by the freezing of snow meltwaters. Two groups of heaVy metals, iron‐based and lead‐based, are identified within the built area of the city of Anadyr’. The spatial distribution of each group coincides with particular types of landscape elements, which reflects both the processes leading to the formation of the icings and the behavior of the different metals when suspended in meltwaters. Icing formation on the whole plays the role of a complex geochemical barrier and leads to the local concentration of chemical elements in mechanical and salt aureoles.

A comprehensive photophysical study is presented which compares the ground- and excited-state properties of four platinum(II) terpyridyl acetylide compounds of the general formula [Pt(tBu3tpy)(CCR)]+, where tBu3tpy is 4,4',4' '-tri-tert-butyl-2,2':6',2' '-terpyridine and R is an alkyl or aryl group. [Ru(tBu3tpy)3]2+ and the pivotal synthetic precursor [Pt(tBu3tpy)Cl]+ were also investigated in the current work. The latter two complexes possess short excited-state lifetimes and were investigated using ultrafast spectrometry while the other four compounds were evaluated using conventional nanosecond transient-absorption spectroscopy. The original intention of this study was to comprehend the nature of the impressive excited-state absorptions that emanate from this class of transition-metal chromophores. Transient-absorbance-difference spectra across the series contain the same salient features, which are modulated only slightly in wavelength and markedly in intensity as a function of the appended acetylide ligand. More intense absorption transients are observed in the arylacetylide structures relative to those bearing an alkylacetylide, consistent with transitions coupled to the pi system of the ancillary ligand. Reductive spectroelectrochemical measurements successfully generated the electronic spectrum of the tBu3tpy radical anion in all six complexes at room temperature. These measurements confirm that electronic absorptions associated with the tBu3tpy radical anion simply do not account for the intense optical transitions observed in the excited state of the Pt(II) chromophores. Transient-trapping experiments using the spectroscopically silent reductive quencher DABCO clearly demonstrate the loss of most transient-absorption features in the acetylide complexes throughout the UV, visible, and near-IR regions following bimolecular excited-state electron transfer, suggesting that these features are strongly tied to the photogenerated hole which is delocalized across the Pt center and the ancillary acetylide ligand.

We report on accurate measurements of the scalar αS and tensor αT polarizabilities of the 5D fine structure levels 5D3/2 and 5D5/2 in Rb.

We report the observation of influence of homogeneous magnetic field on an optical lattice losses of ultracold thulium atoms. The atomic cloud temperature was T = 15 mK. The dependence of trap population on a value of magnetic field has a broad resonance in the low-field region with a center at B = 0.4 G. We also have measured a decrease of optical lattice lifetime in a presence of resonance magnetic field. The observed magnetically-induced trap losses are assumed to be Feshbach resonance which is a dependence of an atomic scattering length on magnetic field.

We discuss current progress in laser cooling of lanthanides (Er, Yb, Dy, Tm etc.) focusing on applications. We describe some important peculiarities taking Thulium atom as an example: Two stage laser cooling, trapping in an optical lattice, anisotropic interactions and spectroscopy of narrow transitions. Specific level structure and presence of magic wavelengths make ultracold Thulium a favorable candidate for optical clock applications. On the other hand, abundance of Feshbach resonances allow to tune interactions in ultracold gases and thus reach quantum degeneracy. It opens intriguing perspectives for novel quantum simulators employing dipole-dipole interactions in an optical lattice.

Technique of the production of thorium ions via laser ablation reported. Trapping ions using quadrupole linear trap with trapping time up to 30 s demonstrated.

We report a new optical technology which enables arbitrarily manipulating amplitudes and phases of a highly-discrete optical spectrum and its application to generating a train of 1.4-fs ultrafast pulses with a repetition-rate exceeding 100 THz.