Li+ and Na+ molybdate crystals are considered promising materials in the rare events physics field due to their high energy resolution and radiation purity. This paper describes the growth details of mixed Li-Na polymolybdate crystal by the low-thermal-gradient Czochralski technique. Li2,6Na3,4Mo9O30 crystals with dimensions up to 70x37x32 mm3 were obtained, their crystal structure was studied and a morphology model was built in VESTA software. DSC studies showed Li2,6Na3,4Mo9O30 compound to be the one with the lowest melting temperature in Li6Mo9O30-Na6Mo9O30 system, indicating it to be the eutectic composition. Photoluminescence was registered in 175-77 K temperature range with emission peak at 700 nm. The generation of the second harmonic was found to be higher than that of the BBO crystal. From all of the above, Li2,6Na3,4Mo9O30 crystal could be considered promising both as a scintillation material and as an element for nonlinear optics.

Li2WO4 single crystals and Mo-doped Li2W1-xMoxO4 (x = 0.0125, 0.05) were grown by the low-thermal-gradient Czochralski technique. Optimal crystallization conditions were determined for obtaining single crystals with a length of 50 mm and a diameter of 30 mm: crystallization rate of 0.5 mm h-1 and rotation rate of 5 rpm. The crystal structure was investigated using powder X-ray diffraction, which confirmed the single-phase nature and trigonal structure (space group R3) for all compositions. Differential scanning calorimetry did not reveal phase transitions in the temperature range 303-1153 K. The influence of partial substitution of W with Mo on the luminescence properties is demonstrated and a correlation between Mo concentration and emission characteristics is established.

This article demonstrates the application of an original technique for single crystal unit cell parameter determination during the certification of a new X-ray diffraction standard Bi4Ge3O12 (BGO) using a conventional laboratory diffractometer equipped with a 2D detector. A BGO crystal weighing 51.86 kg and over 50 cm in length was grown using the LTG CZ method. The dynamics of structural characteristics was studied in the temperature range of 140-480 K by single crystal X-ray diffraction analysis. The cubic unit cell parameters of nine BGO single crystals taken from different areas of the initial sample were determined using the original technique based on the calibration of the goniometer equatorial circumference of small segments according to external standard doublets. The measurements were carried out in the diffraction angle range of 2 theta similar to 120 degrees (MoK alpha-radiation), and the relative error was no more than 5 x 10-5. It was found that the initial BGO sample is homogeneous, and its unit cell parameter values are in the range of 10.5176-10.5183 & Aring;, < a > = 10.5180(5) & Aring;. The thermal expansion of BGO was studied in the range of 100-500 K. It was shown that the absolute increase in cell volume is 8.1 & Aring;3 with a relative increase of 0.7%. The thermal expansion coefficient of BGO at room temperature is 6.39 x 10-6 K-1. The potential use of BGO single crystals as an external and internal standard is demonstrated in the test refinement of Si and Ge poly- and single crystal unit cell parameters.

The use of large scintillating crystals as cryogenic calorimeters was proven to be a promising strategy in the search for the neutrinoless Double Beta Decay (0v(3(3). Such a rare nuclear process would provide crucial information on the nature of the neutrino (i.e. whether it is a Majorana or a Dirac particle) and on the value of its mass. In this work, scintillating crystals of Li2MoO4, Li2MoO4:Ag, and Li2WO4 grown by the Czochralski technique were studied as they are both promising candidates for scintillating cryogenic calorimeters: the former due to 100Mo isotope suitable for 0v(3(3 search, and the latter because of the presence of 6Li for spin dependent dark matter search. Using various spectroscopic techniques, we investigated the scintillating properties of all these crystals and the effect of point defects on their scintillation performances, evaluating the parameters of the traps involved in the scintillation mechanism and demonstrating for the first time that the temperature dependence of the bright burn phenomenon is tightly correlated with the presence of defects responsible for low temperature thermally stimulated luminescence peaks.

AMoRE searches for the neutrinoless double beta decay using 100 kg of enriched ^{100}Mo. Scintillating molybdate crystals coupled with a metallic magnetic calorimeter operate at milli-Kelvin temperatures to measure the energy of electrons emitted in the decay. AMoRE-I is a demonstrator for the full-scale AMoRE, operated at the Yangyang Underground Laboratory for over two years. The exposure was 8.02  kg year (or 3.89  kg_{^{100}Mo} year), and the total background rate near the Q value was 0.025±0.002  counts/keV/kg/year. We observed no indication of 0νββ decay and report a new lower limit of the half-life of ^{100}Mo 0νββ decay as T_{1/2}^{0ν}>2.9×10^{24}  yr at 90% confidence level. The effective Majorana mass limit range is m_{ββ}<(210-610)  meV using nuclear matrix elements estimated in the framework of different models, including the recent shell model calculations.

Abstract The AMoRE collaboration searches for neutrinoless double beta decay of $$^{100}$$ 100 Mo using molybdate scintillating crystals via low temperature thermal calorimetric detection. The early phases of the experiment, AMoRE-pilot and AMoRE-I, have demonstrated competitive discovery potential. Presently, the AMoRE-II experiment, featuring a large detector array with about 90 kg of $$^{100}$$ 100 Mo isotope, is under construction. This paper discusses the baseline design and characterization of the lithium molybdate cryogenic calorimeters to be used in the AMoRE-II detector modules. The results from prototype setups that incorporate new housing structures and two different crystal masses (316 g and 517–521 g), operated at 10 mK temperature, show energy resolutions (FWHM) of 7.55–8.82 keV at the 2.615 MeV $$^{208}$$ 208 Tl $$\gamma $$ γ line and effective light detection of 0.79–0.96 keV/MeV. The simultaneous heat and light detection enables clear separation of alpha particles with a discrimination power of 12.37–19.50 at the energy region around $$^{6}$$ 6 Li $$(n,\alpha )^3$$ ( n , α ) 3 H with Q-value = 4.785 MeV. Promising detector performances were demonstrated at temperatures as high as 30 mK, which relaxes the temperature constraints for operating the large AMoRE-II array.

Bulk Na6Mo11O36 single crystals with dimensions 70*40*20 and 70*40*40 mm3 were obtained by the low-thermal gradient Czochralski technique. The uniformity of the grown boules was assessed using the following characterization techniques: X-ray diffraction (XRD) and differential scanning calorimetry. The crystal structure was thoroughly examined through single-crystal X-ray diffraction (SCXRD). Space group was determined by SCXRD as C2/c (a = 7.2229(1) & Aring;, b = 17.8065(4) & Aring;, c = 22.2789(5) & Aring;, beta = 90.311(1)degrees). Na6Mo11O36 crystals exhibited a strong tendency to formation of twins up to the change of crystallization direction on 90 degrees during the growth process, which is a unique event for Czochralski technique crystal growth. Crystal faceting was studied, and Miller indexes of developed facet families were determined by the XRD method; a reference model of the Na6Mo11O36 crystal was visualized based on obtained data. Optimal growth direction for obtaining uniform bulk Na6Mo11O36 crystals was determined to be [010]. Photoluminescence was registered on a 10 x 10 x 10 mm3 sample from 175 K temperature and below.

Investigation of spontaneous and stimulated Raman scattering in a crystal of sodium dimolybdate, Na2Mo2O7 with an orthorhombic structure is presented. Polarized Raman spectra corresponding to six independent components of the Raman tensor have been obtained. The phonon frequencies were determined and the oscillations were identified by types of symmetry. Raman-laser mode in Na2Mo2O7 has the highest frequency value among the molybdate crystals, equal to 939 cm–1. For the first time, Raman oscillation was obtained on a Na2Mo2O7 crystal when excited by pulses of Nd:YLF laser with a wavelength of 1047 nm and a duration of 25 ps. The Raman gain coefficient at optimal orientation was 12.4 cm/GW, which is one of the highest values for solid-state Raman media. The described studies have shown that the sodium dimolybdate crystal is a promising nonlinear medium for creating a solid-state Raman converter.

AbstractAMoRE-II aims to search for neutrinoless double beta decay ($$0\nu \beta \beta $$ 0 ν β β ) with an array of 423 $$\hbox {Li}_2^{100}\hbox {MoO}_4$$ Li 2 100 MoO 4 crystals operating in the cryogenic system as the main phase of the Advanced Molybdenum-based Rare process Experiment (AMoRE). AMoRE has been planned to operate in three phases: AMoRE-pilot, AMoRE-I, and AMoRE-II. AMoRE-II is currently being installed at the Yemi Underground Laboratory, located approximately 1000 m deep in Jeongseon, Korea. The goal of the experiment is to reach an exclusion half-life sensitivity to the $$0\nu \beta \beta $$ 0 ν β β of $$^{100}$$ 100 Mo on the level of $$T^{0\nu \beta \beta }_{1/2} > 6 \times 10^{26}$$ T 1 / 2 0 ν β β > 6 × 10 26 year that covers completely the inverted Majorana neutrino mass hierarchy region of (15–46) meV. To achieve this, the background level of the experimental configurations and possible background sources of gamma and beta events should be well understood. We have intensively performed Monte Carlo simulations using the GEANT4 toolkit in all the experimental configurations with potential sources. We report the estimated background level that meets the $$10^{-4}$$ 10 - 4 counts/(keV$$\cdot $$ · kg$$\cdot $$ · year) requirement for AMoRE-II in the Region Of Interest (ROI) and show the projected half-life sensitivity based on the simulation study.

We present the development of a dual-detector system designed for investigating the spectral shape of forbidden non-unique beta decays. Two PbMoO 4 scintillating crystals were carefully prepared for heat and light detection at milli-Kelvin (mK) temperatures. Notably, one crystal was synthesized using archaeological lead, while the other was composed of natural modern lead. The significance of employing two crystals lies in their identical dimensions and proximity, resulting in similar environmental background exposure. Their distinct internal radioactivities, particularly associated with 210 Pb, introduce a distinguishing factor between the spectra measured in the two detectors. Our detection method includes achieving clear particle identification through the relative amplitudes of light and heat signals for both crystals. This report compares the electron-induced spectra within energy regions both below and above the endpoint of 210 Bi beta decay. This comparative study provides valuable insights into an exact measurement of the 210 Bi decay spectrum, forbidden non-unique beta decay.

Stimulated Raman scattering was obtained in anisotropic Na 2 Mo2 O 7 crystal with frequency shift of 37 cm -1 when excited by picosecond pulses at wavelength of 1047 nm. Raman gain coefficient was measured depending on the orientation of the crystal.

The AMoRE-II experiment will search for the 0νββ decay of 100Mo nuclei using molybdate crystal scintillators, operating at milli-Kelvin (mK) temperatures, with a total of 80 kg of 100Mo. The background goal for the experiment is 10–4 counts/keV/kg/year in the region of interest around the 0νββ decay Q-value of 3,034 keV. To achieve this level, the rate of background signals arising from emissions produced by decays of radioactive impurities in the detector and shielding materials must be strictly controlled. To do this, concentrations of such impurities are measured and are controlled through materials selection and purification. In this paper, we describe the design and the construction materials used to build the AMoRE-II detector and shielding system, including active and passive shielding, the cryostat, and the detector holders and instrumentation, and we report on measurements of radioactive impurities within candidate and selected materials.

Стандартная энтальпия образования димолибдата натрия определена методом калориметрии растворения на основании измеренных энтальпий растворения Na2CO3, MoO3, Na2Mo2O7 в 0.2 M растворе NaOH и литературных данных: ∆fH0(Na2Mo2O7, 298.15 K) = −2245.3 ± 6.3 кДж/моль. С использованием цикла Борна–Габера рассчитана энтальпия решетки: –54730 кДж/моль. Показано, что длина волны люминесцентного излучения уменьшается от 650 нм до 540 нм при переходе от молибдата натрия к вольфрамату натрия, при этом энтальпия решетки уменьшается от –54730 кДж/моль (Na2Mo2O7) до –49030 кДж/моль (Na2W2O7). Температурная зависимость теплоемкости димолибдата натрия определена в области температур 320–785 K. Показано, что в этом интервале отсутствуют фазовые переходы.

Transparent Li4Mo5O17 crystals with dimensions 60 x 30 x 20 mm were grown by low-thermal-gradient Czo-chralski technique. Optimal growth parameters were determined. According to SCXRD, Li4Mo5O17 compound crystallizes in the triclinic space group of P 1 and the unit cell parameters at 150 K are a = 6.7596(2) angstrom, b = 9.4546(3) angstrom, c = 10.7909(3) angstrom, alpha = 73.1610(10)degrees, 8 = 88.8810(10)degrees, gamma = 69.7460(10)degrees, V = 616.75(3) angstrom 3. Uniformity of obtained crystals was confirmed by XRD analysis. Li4Mo5O17 crystal structure and cell parameters were studied by SCXRD. Li4Mo5O17 melting point at 546 degrees C was determined by DSC curve in 300-1000 K range. Luminescence was registered with peak maximum 670 nm at 370 nm excitation and 645 nm at 300 nm excitation.

We report a study on the background of the Advanced Molybdenum-Based Rare process Experiment (AMoRE), a search for neutrinoless double beta decay (\znbb) of $^{100}$Mo. The pilot stage of the experiment was conducted using $\sim$1.9 kg of \CAMOO~ crystals at the Yangyang Underground Laboratory, South Korea, from 2015 to 2018. We compared the measured $\beta/\gamma$ energy spectra in three experimental configurations with the results of Monte Carlo simulations and identified the background sources in each configuration. We replaced several detector components and enhanced the neutron shielding to lower the background level between configurations. A limit on the half-life of $0\nu\beta\beta$ decay of $^{100}$Mo was found at $T_{1/2}^{0\nu} \ge 3.0\times 10^{23}$ years at 90\% confidence level, based on the measured background and its modeling. Further reduction of the background rate in the AMoRE-I and AMoRE-II are discussed.

Na2Mo2xW2(1 − x)O7 (x = 0..1 with step 0.1) compositions were obtained by solid-state synthesis and spontaneous crystallization. The sample series were studied by XRD, Raman, DSC and SEM methods. The obtained data indicates formation of solid solutions, with unit cell gradually increasing with increasing tungsten ratio. A refined Na2Mo2O7 - Na2W2O7 phase diagram with unlimited miscibility was constructed. The solidus line was built based on DSC data and the liquidus line was constructed based on spontaneous crystallization experiments data. A luminescence study showed possibility of emission color variation in Na2Mo2xW2(1 − x)O7 solid solutions in dependence from excitation wavelength.

The heat capacity of zinc tungstate was determined by relaxation calorimetry in the range of 2.6–40 K. The heat capacity was extrapolated to zero temperature, and the characteristic Debye temperature at zero temperature was determined. The experimental heat capacities presented in the literature were estimated. The values of thermodynamic functions in the range 0–301 K were refined.

The current experiments searching for neutrinoless double- β ( 0νββ ) decay also collect large statistics of Standard Model allowed two-neutrino double- β ( 2νββ ) decay events. These can be used to search for Beyond Standard Model (BSM) physics via 2νββ decay spectral distortions. 100Mo has a natural advantage due to its relatively short half-life, allowing higher 2νββ decay statistics at equal exposures compared to the other isotopes. We demonstrate the potential of the dual read-out bolometric technique exploiting a 100Mo exposure of 1.47 kg × years, acquired in the CUPID-Mo experiment at the Modane underground laboratory (France). We set limits on 0νββ decays with the emission of one or more Majorons, on 2νββ decay with Lorentz violation, and 2νββ decay with a sterile neutrino emission. In this analysis, we investigate the systematic uncertainty induced by modeling the 2νββ decay spectral shape parameterized through an improved model, an effect never considered before. This work motivates searches for BSM processes in the upcoming CUPID experiment, which will collect the largest amount of 2νββ decay events among the next-generation experiments.

Abstract The current experiments searching for neutrinoless double- $$\beta $$ β ( $$0\nu \beta \beta $$ 0 ν β β ) decay also collect large statistics of Standard Model allowed two-neutrino double- $$\beta $$ β ( $$2\nu \beta \beta $$ 2 ν β β ) decay events. These can be used to search for Beyond Standard Model (BSM) physics via $$2\nu \beta \beta $$ 2 ν β β decay spectral distortions. 100Mo has a natural advantage due to its relatively short half-life, allowing higher $$2\nu \beta \beta $$ 2 ν β β decay statistics at equal exposures compared to the other isotopes. We demonstrate the potential of the dual read-out bolometric technique exploiting a 100Mo exposure of 1.47 kg $$\times $$ × years, acquired in the CUPID-Mo experiment at the Modane underground laboratory (France). We set limits on $$0\nu \beta \beta $$ 0 ν β β decays with the emission of one or more Majorons, on $$2\nu \beta \beta $$ 2 ν β β decay with Lorentz violation, and $$2\nu \beta \beta $$ 2 ν β β decay with a sterile neutrino emission. In this analysis, we investigate the systematic uncertainty induced by modeling the $$2\nu \beta \beta $$ 2 ν β β decay spectral shape parameterized through an improved model, an effect never considered before. This work motivates searches for BSM processes in the upcoming CUPID experiment, which will collect the largest amount of $$2\nu \beta \beta $$ 2 ν β β decay events among the next-generation experiments.

Two-photon absorption was investigated in Na 2 Mo 2 O 7 anisotropic crystal under irradiation with picosecond laser pulses at 523 nm. The value of the coefficient of the two-photon absorption was measured to be 6.7 and $0.13 \mathrm{~cm} / \mathrm{GW}$, depending on the orientation of the crystal.