Pyrex Cell Research Articles

Celebrating the the art of chemistry in the International Year of Glass

Grateful for glass The United Nations declared that 2022 is the International Year of Glass , and Newscripts would like to take this opportunity to celebrate the crucial contributions of scientific glassware to chemistry. With items as varied as Pyrex flasks and cell phone screens, glass gear has long been a mainstay for researchers around the globe. Chemists in particular owe a debt of gratitude to vitreous accoutrements and the glassblowers who craft them, says Catherine M. Jackson, a chemist and historian of science at the University of Oxford. Her research centers on the evolution of the chemical sciences in the 19th century, the era when scientists took the first forays into organic synthesis and the 3D structures of molecules. “It’s through the agency of glassware that chemists first appreciate the molecular nature of matter,” Jackson tells Newscripts. Specialized glassware enabled scientists to observe chemical worlds enclosed in transparent vessels.

A highly drift-stable atomic magnetometer for fundamental physics experiments

We report the design and performance of a nonmagnetic drift stable optically pumped cesium magnetometer with a measured sensitivity of 35 fT at 200 s integration time and stability below 50 fT between 70 and 600 s. The sensor is based on the nonlinear magneto-optical rotation effect: in a Bell–Bloom configuration, a higher order polarization moment (alignment) of Cs atoms is created with a pump laser beam in an anti-relaxation coated Pyrex cell under vacuum, filled with Cs vapor at room temperature. The polarization plane of light passing through the cell is modulated due the precession of the atoms in an external magnetic field of 2.1 μT, used to optically determine the Larmor precession frequency. Operation is based on a sequence of optical pumping and observation of freely precessing spins at a repetition rate of 8 Hz. This free precession decay readout scheme separates optical pumping and probing and, thus, ensures a systematically highly clean measurement. Due to the residual offset of the sensor of <15 pT together with negligible crosstalk of adjacent sensors, this device is uniquely suitable for a variety of experiments in low-energy particle physics with extreme precision, here as a highly stable and systematically clean reference probe in search for time-reversal symmetry violating electric dipole moments.

An experimental study of the gas-phase reaction between Cl atoms and trans-2-pentenal: Kinetics, products and SOA formation

The gas-phase reaction of trans-2-pentenal (T2P) with Cl atoms was studied at atmospheric pressure and room temperature. A rate coefficient of (2.56 ± 0.83) × 10-10 cm3 molecule-1 s-1 was obtained using the relative rate method and isoprene, cyclohexane and ethanol as reference compounds. The kinetic study was carried out using a 300-L Teflon bag simulation chamber (IMT Lille Douai-France) and a 16-L Pyrex cell (UCLM-Ciudad Real-Spain), both coupled to the Fourier transform infrared (FTIR) technique. Gas-phase products and secondary organic aerosol (SOA) formation were studied at UCLM using a 16-L Pyrex cell and a 264-L quartz simulation chamber coupled to the FTIR and gas-chromatography-mass spectrometry (GC-MS) techniques. HCl, CO, and propanal were identified as products formed from the studied reaction and quantified by FTIR, the molar yield of the latter being (5.2 ± 0.2)%. Formic acid was identified as a secondary product and was quantified by FTIR with a yield of (6.2 ± 0.4)%. In addition, 2-chlorobutanal and 2–pentenoic acid were identified, but not quantified, by GC-MS as products. The SOA formation was investigated using a fast mobility particle sizer spectrometer. The observed SOA yields reached maximum values of around 7% at high particle mass concentrations. This work provides the first study of the formation of gaseous and particulate products for the reaction of Cl with T2P. A reaction mechanism is suggested to explain the formation of the observed gaseous products. The results are discussed in terms of structure-reactivity relationship, and the atmospheric implications derived from this study are commented as well.

Oxidation of n-hexane in the vicinity of the auto-ignition temperature

The present study examines the possibility of inerting flammable mixtures (making the mixtures non-explosive/non-flammable) using a long duration thermal process close to but below the auto-ignition temperature. Experiments were performed in a stainless steel cell and a Pyrex cell. A Mid-IR FTIR spectrometer, a UV–vis spectrometer and several IR laser diodes were employed to monitor the gas-phase composition. Experiments were performed for n-hexane-air mixtures with Φ = 0.67–1.35. The temperature and pressure were T = 420–500 K and P = 37–147 kPa. Experiments were performed over period of up to 7200 s. At temperatures close to 420 K, the chemical activity is characterized by a slow and constant reaction rate. At temperatures close to 500 K, the reaction proceeds in two-phases: 1) rapid production of CO2, CO and carbonyls, identified as hydroperoxy-ketones, followed by 2) a period of slower production of CO2 and H2O and consumption of hydroperoxy-ketones. At the end of the thermal treatment, the possibility of igniting the mixtures using a large hot surface (representative of low-temperature ignition source) and a stationary concentrated hot surface (representative of high-temperature ignition source) was tested. The low-temperature flammability was verified by rapidly increasing the temperature of the test cell wall whereas the high-temperature flammability was verified by turning on a glow plug. The inerting strategy seems effective in preventing the low-temperature ignition but high-temperature ignition was always observed. .

UV absorption cross sections between 290 and 380 nm of a series of furanaldehydes: Estimation of their photolysis lifetimes

Furanaldehydes, such as 2-furanaldehyde (also known as furfural), 3-furanaldehyde and 5-methyl-2-furanaldehyde, are aromatic aldehydes which can be present in the atmosphere as primary and secondary pollutants. The atmospheric removal initiated by sunlight for these species is not well-known in the solar actinic region (at λ > 290 nm), mainly due to the absence of data concerning the UV absorption cross sections (σλ) and photolysis frequencies (Ji(z,θ)). In this work σλ for the mentioned furanaldehydes have been determined between 290 and 380 nm at room temperature for the first time. Experiments were performed in an absorption jacketed Pyrex cell, employing a deuterium lamp as irradiation source and a CCD detector. The obtained absorption spectra exhibit absorption maxima around 320 nm with absolute absorption cross sections of 1.13, 0.75 and 1.14 × 10−19 cm2 molecule−1 for 2-furanaldehyde, 3-furanaldehyde and 5-methyl-2-furanaldehyde, respectively. The reported UV absorption cross sections were used to provide estimates of Ji(z,θ) and, therefore, estimates of the lifetime (τhν) due to this atmospheric removal process, under different solar radiation situations. Estimated τhν have been compared with the lifetimes due to the homogeneous reaction with the main diurnal tropospheric oxidants. The results obtained suggest that photolysis in the actinic region can be the main degradation pathway for these furanaldehydes when assuming a quantum yield (Φλ) of unity and the maximum solar actinic flux, while photolysis can compete with the reaction of OH radicals when assuming Φλ = 0.1. On the contrary, the removal of all three furanaldehydes by the reactions with OH radicals becomes more important than the UV photolysis under low solar actinic flux conditions independently of Φλ. If the emission source of these furanaldehydes also occurs during the nighttime NO3 radicals will dominate the elimination process of these species.

Pressure broadening and frequency shift of the 5S1/2 → 5D5/2 and 5S1/2 → 7S1/2 two photon transitions in 85Rb by the noble gases and N2

Doppler free two photon absorption spectroscopy was employed to measure the pressure broadening and frequency shift rates of the 5S1/2 (F = 3) → 5D5/2 (F = 5, 4, 3, 2, 1) (778.105 nm) and the 5S1/2 (F = 2) → 7S1/2 (F = 2) (760.126 nm) two photon transitions in 85Rb by the noble gases and N2. To our knowledge, these rates are reported on for the first time. The self-broadening and shift rate of the 5S1/2 (F = 3) → 5D5/2 (F = 5, 4, 3, 2, 1) transition and self -broadening rate of the 5S1/2 (F = 2) → 7S1/2 (F = 2) transition were also measured. The temperature dependence of the self-frequency shift (Rb-Rb collisions) of these transitions is presented. Helium diffusion rates through Quartz and Pyrex cells are also calculated and the implication of helium diffusion through glass vapor cells is discussed in regards to atomic frequency standards based on these transitions. Experimental pressure broadening and shift rates are compared to theoretically calculated rates assuming a 6, 8 or 6, 8, 10 difference potential and pseudo potential model. Reasonable agreement is achieved between experimental and theoretical values.

Light desorption from an yttrium neutralizer for Rb and Fr magneto-optical trap loading.

We present here the first evidence of photodesorption induced by low-intensity non-resonant light from an yttrium thin foil, which works as a neutralizer for Rb and Fr ions beam. Neutral atoms are suddenly ejected from the metal surface in a pulsed regime upon illumination with a broadband flash light and then released in the free volume of a pyrex cells. Here atoms are captured by a Magneto-Optical Trap (MOT), which is effectively loaded by the photodesorption. Loading times of the order of the flash rise time are measured. Desorption is also obtained in the continuous regime, by exploiting CW visible illumination of the metallic neutralizer surface. We demonstrate that at lower CW light intensities vacuum conditions are not perturbed by the photodesorption and hence the MOT dynamics remains unaffected, while the trap population increases thanks to the incoming desorbed atoms flux. Even with the Y foil at room temperature and hence with no trapped atoms, upon visible illumination, the number of trapped atoms reaches 10(5). The experimental data are then analyzed by means of an analytical rate equation model, which allows the analysis of this phenomenon and its dynamics and allows the determination of critical experimental parameters and the test of the procedure in the framework of radioactive Francium trapping. In this view, together with an extensive investigation of the phenomenon with (85)Rb, the first demonstration of the photodesorption-aided loading of a (210)Fr MOT is shown.

Diffusion and photodesorption of molecular gases in a polymer organic film

We report the first study of photodesorption of various molecular gases from a polymer organic film. This study was carried out in a Pyrex cell whose inner surface was covered by a polydimethyl-siloxane (PDMS) compound. The cell was illuminated by a flash or a CW halogen lamp. The molecular gas composition was analyzed with a mass spectrometer. We observed the variation of the molecular gas density due to photodesorption in a vapor cell as a function of illumination time, intensity, wavelength and temperature of the coating. We have observed that the desorption rate strongly depends on the light wavelength, with a threshold at about 500 nm. A linear dependence of the desorption rate on the incident light intensity has been found. This means that this effect is not caused by the direct heating of the surface and is non-thermal in nature. We have found that, under continuous illumination of the cell by a halogen lamp, the molecular photodesorption yield shows a fast decay curve, which is then followed by a long diffusion tail. The molecular photodesorption yield drops rapidly with decreasing temperature because the diffusion in the polymer in a glassy state decreases. These results are a clear indication that bulk diffusion plays an important role in the observed molecular photodesorption process. This study could be useful for constructing light-driven sources of molecules.

Electrochemical Properties of TiO2 Electrode Prepared by Various Methods

Abstract Thin transparent TiO2 layers were created on the conductive ITO glass by means of the templated sol-gel technique and by the subsequent calcination at 450° C. The sol-gel method using molecular templating is based on a chemical process utilizing hydrolysis and polycondesation of metal alkoxides in the core of reverse micelles which allows a production of uniform particles in layers. The sol-gel method was chosen by reason of the sol-gel layers electrodes are transparent and possess very stabile surface. For the preparation of the thin sol-gel TiO 2 films, numerous deposition techniques were applied. This contribution is focused on the study of structural and photo-electrochemical properties of the sol-gel nanostructured layers deposited by two various techniques (a dip-coating and an inkjet printing). The sol's viscosity, concentration, solvent volatility, speed of pulling etc. may influence the final structural properties of layers, such as film thickness, nanoparticles size and surface morphology. The surface properties were determined by XRD, Raman, SEM, AFM and UV-Vis analyses. Photo-induced electrochemical properties were measured by potentiodynamic methods in the three-compartment electrochemical cell. This Pyrex cell contained supporting electrolyte (0.1 M Na2SO4) and the TiO2/ITO electrode was used as a working electrode. As an UV source the polychromatic mercury lamp was employed and the wavelength of the incident light was focused by an interference filter on 365 nm.

Optical stabilization of Rb vapor density above thermal equilibrium

We stabilize the Rb vapor density above its thermal equilibrium value in sealed glass cells, which are generally used in atomic physics experiments. The method relies on light-induced desorption of Rb atoms from dielectric surfaces. The process does not demand high light intensities so that LEDs or laser diodes can be used as desorbing sources. The experiments are carried out in Pyrex cells either coated with a polydimethylsiloxane film or containing a porous glass sample. Under illumination both the organic coating and the porous sample release a large amount of Rb atoms into the cell volume. We show that the Rb vapor density can be maintained to a preset value, using a desorbing light intensity controlled by a feedback signal given by the Rb absorption or fluorescence level. Moreover, we find that the stabilization technique does not depend on the microscopic mechanisms underlying photodesorption.

Modification of glass cell walls by rubidium vapor

It has long been known that the inner walls of freshly manufactured glass cells filled with a few droplets of alkali metal undergo a ``curing'' process, where the properties of the cell wall change over a period of days to weeks. We report quantitative studies of ``curing'' in Pyrex cells filled with rubidium metal. Our experiment shows that at $94\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$, the surface of Pyrex glass adsorbs about $3\ifmmode\times\else\texttimes\fi{}{10}^{15}$ rubidium atoms per ${\text{cm}}^{2}$, which is equivalent to 6--7 monolayers of liquid rubidium.

Raman spectroscopic measurements of synthetic gas hydrates in the ocean

A Raman spectrometer extensively modified for deep ocean use was used to measure synthetic hydrates formed in an ocean environment. This was the first time hydrates formed in the ocean have been measured in situ using Raman spectroscopy. Gas hydrates were formed in situ in the Monterey Bay by pressurizing a Pyrex cell with various gas mixtures. Raman spectra were obtained for sI methane hydrate and sII methane + ethane hydrate. Gas occlusion resulting from rapid gas growth of methane hydrate was measured immediately after formation. The Raman shift for methane free gas was coincident with that of methane in the small 5 12 hydrate cage. The methane Raman peak widths were used to discriminate between methane in the free gas and hydrate phase. Methane + ethane sII hydrate was formed for 43 days on the seafloor. In this case, gas occlusion was not measured when the gas hydrates were allowed to form over an extended time period. Equivalent Raman spectra were obtained for the in situ and laboratory-formed sII methane + ethane hydrates, under similar p, T, and x conditions. With the Raman spectrometer operating in the ocean, seawater contributes to the Raman spectra obtained. Both the Raman bands for the sulfate ion and water were used to qualitatively determine the distribution of water phases measured (hydrate, seawater) in the Raman spectra.

Desorption of Rb and Cs from PDMS induced by non resonant light scattering

Simultaneous light-induced desorption of rubidium and cesium atoms has been observed in polydimethylsiloxane (PDMS) coated Pyrex cells at room temperature and at low light intensity. The two alkali atoms show the same dynamics and the same dependence on the desorbing light frequency. No competition in the free sites occupancy exists. An interpretation of the experimental results in terms of non-resonant light scattering from the PDMS coating is discussed.

Doppler-free spectroscopy of metastable calcium in a discharge heat pipe

We report on Doppler-free frequency modulation spectroscopy and polarization spectroscopy in a discharge heat pipe of yet unexplored transitions connecting the metastable $^{3}P_{2}(4s4p)$ state of calcium atoms with the multiply excited states $^{3}P_{2}(4p4p)$ and $^{3}D_{3}(4s3d)$. Calcium vapor is efficiently produced in a heat pipe operating in a small Pyrex cell filled with $2\phantom{\rule{0.3em}{0ex}}\text{torr}$ of neon. A dc discharge running at $500\phantom{\rule{0.3em}{0ex}}\mathrm{V}$ efficiently populates the metastable triplet states. Narrow resonances with bandwidths of a few tens of MHz with excellent signal-to-noise ratios are observed, well suited as references for laser frequency stabilization. Examination of the Zeeman shifts lets us determine the Land\'e $g$ factors of the excited states and compare them with the predictions based on the Russel-Saunders coupling scheme. We describe an economic, simple, and robust experimental setup that should work for other alkaline-earth-metal atoms like Mg and Sr, as well as for other solid elements with insufficient vapor pressures at room temperature.

Influence of the history of a melt on the electrical resistivity of cadmium–antimony liquid alloys

Miller, Paces and Komarek (MPK) [Trans. Metall Soc. AIME 230 (1964) 1557] observed an influence of the history of a melt on the electrical resistivity of several cadmium–antimony alloys. In this work we complete the experimental work of MPK with new accurate experiments in order to verify the existence of the phenomenon and to precise by defining the conditions where it appears. We used three important improvements on the experimental design of MPK. First we used quartz cells instead of pyrex cells used by MPK so allowing the heating of the melt well above the temperature of 530 °C attained by MPK. Secondly our experimental design allows to mix mechanically the liquid alloy in order to achieve a macroscopic homogeneity of the melt. Finally we measure simultaneously the thermopower of the Cd60–Sb40 liquid alloy. The time evolution of our experiment is fully described with our conclusions.

Wall relaxation of 3He in spin-exchange cells.

The 3He longitudinal spin-relaxation rate T1-1 is crucial for production of highly polarized 3He by spin-exchange optical pumping. We show that T1-1 is increased by a factor of 2-20 solely by exposure of spin-exchange cells to a few-kG magnetic field. The original T1-1 can be restored by degaussing the cell. The effect is attributed to magnetic surface sites and has been observed in both Pyrex and aluminosilicate-glass cells. Our results both advance the understanding of wall relaxation and demonstrate the use of 3He as an extremely sensitive probe of surface magnetism.

A new class of photo-induced phenomena in siloxane films

The light induced atomic desorption effect, known as LIAD, is observed whenever Pyrex cells, coated with siloxane films and containing alkali atoms, are illuminated. LIAD is a non-thermal phenomenon and it can be observed even with very weak light intensities. We show that the simultaneous contribution to the photo-emission of atoms adsorbed both at the film surface and within the film must be taken into account in order to fit the experimental data. We demonstrate that both the desorption efficiency and the diffusion coefficient of the alkali atoms embedded in the dielectric film depend on the desorbing light intensity. These features characterize a new class of photo-induced phenomena whose analysis gives new insights in the comprehension of the atom-surface interaction and of the atom-bulk diffusion and opens interesting perspectives for applications.

Sol-gel coated glass cells for spin-exchange polarized He3

We have developed a high-purity sol-gel coating for the interior surface of glass cells used for polarizing He3 by spin-exchange optical pumping. The coating is designed to minimize spin relaxation due to wall collisions. A longitudinal spin-relaxation time T1 in a sol-gel coated Pyrex cell of 344±8 h was achieved, the longest T1 we have ever recorded for a gaseous sample. Repeated trials indicated that the coating was quite robust. Results using an uncoated Pyrex cell were also quite good, although inferior to the performance of the coated cell.

Coatings for optical pumping cells and short-term storage of hyperpolarized xenon

For a number of years now, siloxanes have been the materials of choice for coating vessels used in the production and short-term storage of hyperpolarized xenon. The methods used to apply this material, however, often vary from one research group to another and it is commonly reported that it is difficult to obtain cells with consistently long spin-lattice relaxation times (T1) and high-polarization levels. In a series of controlled experiments individual production variables were altered and optimized, leading to improved protocols for the reliable production of high-quality siloxane-coated cells. During these studies we discovered that the surface-induced relaxation rates in bare and coated Pyrex cells differ profoundly. This information on Xe relaxation helps to define the limits on the way pumping cells can be improved and suggests the need for further fundamental work on relaxation mechanisms.

Pressure-Dependent Yields and Product Branching Ratios in the Broadband Photolysis of Chlorine Nitrate

The photolysis of chlorine nitrate was studied using broadband flash photolysis coupled with long-path ultraviolet−visible absorption spectroscopy. Branching ratios for the Cl + NO3 and ClO + NO2 product channels were determined from time-dependent measurements of ClO and NO3 concentrations. Yields of the ClO and NO3 products displayed a dependence on the bath gas density and the spectral distribution of the photolysis pulse. Product yields decreased with increasing bath gas density regardless of the spectral distribution of the photolysis pulse; however, the decrease in product yield was much more pronounced when photolysis was limited to longer wavelengths. For photolysis in a quartz cell (λ > 200 nm) the yield decreased by a factor of 2 over the pressure 10−100 Torr. In a Pyrex cell (λ > 300 nm), the yield decreased by a factor of 50 over the same pressure range. When photolysis was limited to λ > 350 nm, the yield decreased by a factor of 250. Branching ratios for the photolysis channels [ClONO2 + hν → ClO + NO2 (1a) and ClONO2 + hν → Cl + NO3 (1b)] were determined from the relative ClO and NO3 product yields at various pressures. Although the absolute product yield displayed a pressure dependence, the branching between the two channels was independent of pressure. The relative branching ratios (assuming negligible contributions from other channels) are 0.61 ± 0.20 for channel 1a and 0.39 ± 0.20 for channel 1b for photolysis with λ > 200 nm and 0.44 ± 0.08 for channel 1a and 0.56 ± 0.08 for channel 1b for photolysis with λ > 300 nm. The implications of these results for the chemistry of the lower stratosphere are discussed.