Evaporation of levitating microdroplets containing nanoparticles: luminescent Gd2O3:Er3+, TiO2, polystyrene; illumination with 806 nm laser from below

Microdroplets of suspension were levitated in a linear quadrupole trap and studied similarly as described e.g. in Y. Shopa et al., JQSRT 296 (2023), but illumination with an 806 nm diode laser (CW, ~1.5 W), which excited luminescence by up-conversion, was provided (vertically) from below. In 2023, its polarization was s+p (~45deg) and from the beginning of 2024, it was p. In some experiments, the droplet was additionally illuminated with a 512 nm diode laser with p polarisation. The suspended phase consisted of nanoparticles of Gd2O3:Er3+ of several concentrations, and for comparison, polystyrene of 1 micrometer diameter and TiO2 of 100 nm diameter. The continuous phase consisted of diethylene (2EG), triethylene (3EG), and tetraethylene (4EG) glycols. The data is divided into the folders correspondingly. Two groups of spectral lines were (usually) visible (green (stronger) and red). We followed the temporal evolution of several selected lines, both in luminescence and in scattering at right angle (usually 538, 548, 553, 562, 633, 654, 661, 675, 682, 783, 806 nm): files *-Spectra.csv, where * (in hh_mm_ss format) always denotes the time of measurement file creation. Simultaneously the shadow image of the droplet was recorded (non-coherent light, 633 nm LED) - in some cases, a movie: *_Shadow-*.avi is provided. The droplet radius was measured by fitting an ellipse to the shadow edge. The ellipse parameters temporal evolution are stored in *-Shadow.pdf files: time, mean diameter (mean of the ellipse axes), long axis rotation, X and Y of the centre, long and short axis, border length, X and Y of “the centre of mass” of the border, fitting error. The microdroplet's vertical position was stabilised with a DC field. The corresponding voltage variation and other stabilisation system parameters are stored in *.csv files: KeyStab: 0 – stabilisation off, 2 – on, k_PID – proportionality parameter of the software voltage regulator, freq – trapping AC field frequency. In some cases, partially concurrently light was collected at a right angle with a PMT for the green 512 or 806 nm laser. The photon count rate is stored in *-CRM.csv files. Time stored in corresponding files was synchronised. In-focus movies (see readme.txt for details) of the evaporating microdroplet were recorded for certain experiments to illustrate its evolution – no synchronisation is available. It must be kept in mind that the observed image is for the most part laser speckle. The "Laser on/off" pertains to the 806 nm laser. Further details can be found in the readme.txt files in the corresponding folder. (No)_th_spectrum.csv represents the ith recorded spectrum from the corresponding experiment. The parameters of the Gd2O3:Er3+ samples can be found in the .pptx files.

悬浮液微滴在直线四极阱中被悬浮并进行了研究，其方法类似于Y. Shopa等人在JQSRT 296（2023）中所述，但采用806 nm二极管激光器（连续波，约1.5 W）从下方进行垂直照射，通过上转换激发荧光。2023年，其偏振态为s+p（约45度），而从2024年初开始变为p。在某些实验中，微滴还额外用512 nm二极管激光器以p偏振进行照射。悬浮相由多种浓度的Gd2O3:Er3+纳米颗粒组成，为比较，还包括直径为1微米的聚苯乙烯和直径为100 nm的TiO2。连续相由二乙二醇（2EG）、三乙二醇（3EG）和四乙二醇（4EG）组成。数据被相应地分为文件夹。两组光谱线（通常为绿色（较强）和红色）可见。我们追踪了数条选定光谱线的时序演化，包括在荧光和正交散射（通常为538、548、553、562、633、654、661、675、682、783、806 nm）中的演化：文件*-Spectra.csv，其中*（hh_mm_ss格式）始终表示测量文件创建的时间。同时记录了微滴的阴影图像（非相干光，633 nm LED），在某些情况下，还提供了电影：*_Shadow-*.avi。通过拟合阴影边缘的椭圆来测量微滴半径。椭圆参数的时序演化存储在*-Shadow.pdf文件中：时间、平均直径（椭圆轴的平均值）、长轴旋转、X和Y轴中心、长轴和短轴、边长、边界的质心X和Y坐标、拟合误差。通过直流电场稳定微滴的垂直位置。相应的电压变化和其他稳定系统参数存储在*.csv文件中：KeyStab：0 – 稳定关闭，2 – 打开，k_PID – 软件电压调节器的比例参数，freq – 捕获交流场频率。在某些情况下，与绿色512 nm或806 nm激光同时收集正交方向的光子，存储在*-CRM.csv文件中的光子计数率。对应文件中存储的时间进行了同步。某些实验记录了蒸发微滴的聚焦电影（详见readme.txt文件中的详细说明）以说明其演化过程——没有同步信息可用。必须注意，观察到的图像主要是激光斑点。'Laser on/off' 指的是806 nm激光。更详细的信息可在相应文件夹中的readme.txt文件中找到。(_No)_th_spectrum.csv表示来自相应实验的第i条记录的光谱。Gd2O3:Er3+样品的参数可在.pptx文件中找到。