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Controlling and manipulating individual quantum systems in solids underpins the growing interest in development of scalable quantum technologies1, 2. Recently, hexagonal boron nitride (hBN) has garnered significant attention in quantum photonic applications due to its ability to host optically stable quantum emitters3-7. However, the large band gap of hBN and the lack of efficient doping inhibits electrical triggering and limits opportunities to study electrical control of emitters. Here, we show an approach to electrically modulate quantum emitters in an hBN–graphene van der Waals heterostructure. We show that quantum emitters in hBN can be reversibly activated and modulated by applying a bias across the device. Notably, a significant number of quantum emitters are intrinsically dark, and become optically active at non-zero voltages. To explain the results, we provide a heuristic electrostatic model of this unique behaviour. Finally, employing these devices we demonstrate a nearly-coherent source with linewidths of ~ 160 MHz. Our results enhance the potential of hBN for tunable solid state quantum emitters for the growing field of quantum information science.

Two-dimensional hexagonal boron nitride offers intriguing opportunities for advanced studies of light–matter interaction at the nanoscale, specifically for realizations in quantum nanophotonics. He...

Atomically thin monolayers of transition metal dichalcogenides (TMDs) have emerged as a promising class of novel materials for optoelectronics and nonlinear optics. However, the intrinsic nonlinearity of TMD monolayers is weak, limiting their functionalities for nonlinear optical processes such as frequency conversion. Here we boost the effective nonlinear susceptibility of a TMD monolayer by integrating it with a resonant dielectric metasurface that supports pronounced optical resonances with high quality factors: bound states in the continuum (BICs). We demonstrate that a WS2 monolayer combined with a silicon metasurface hosting BICs exhibits enhanced second-harmonic intensity by more than 3 orders of magnitude relative to a WS2 monolayer on top of a flat silicon film of the same thickness. Our work suggests a pathway to employ high-index dielectric metasurfaces as hybrid structures for enhancement of TMD nonlinearities with applications in nonlinear microscopy, optoelectronics, and signal processing.

Quantum emitters in hexagonal boron nitride (hBN) flakes have recently emerged as a promising platform for nanophotonic and quantum applications. The solvent-exfoliation process of these flakes has, however, remained largely unexplored. In this work, we demonstrate a surfactant-assisted exfoliation technique in an aqueous solution to exfoliate a variety of commercially available hBN powders into hBN nanoflakes. We show that the selection of hBN powder greatly impacts the optical properties of the resultant quantum emitters embedded in exfoliated hBN nanoflakes. We find that the sample with the best optical performance also shows the lowest impurity levels in its starting hBN powder. Our study provides further insight into quantum emitter fabrication in hBN and tailoring of their optical properties.

Single-photon emitters in hexagonal boron nitride (hBN) are promising constituents for integrated quantum photonics. Specifically, engineering these emitters in large-area, high-quality, exfoliated hBN is needed for their incorporation into photonic devices and two dimensional heterostructures. Here, we report on two different routes to generate high-density quantum emitters with excellent optical properties-including high brightness and photostability. We study in detail high-temperature annealing and plasma treatments as an efficient means to generate dense emitters. We show that both an optimal oxygen flow rate and annealing temperature are required for the formation of high-density quantum emitters. In parallel, we demonstrate that the plasma treatment in various environments, followed by standard annealing is also an effective route for emission engineering. Our work provides vital information for the fabrication of quantum emitters in high-quality, exfoliated hBN flakes and paves the way toward the integration of the quantum emitters with photonic devices.

The emergence of interlayer excitons (IEs) from atomic layered transition metal dichalcogenides (TMDCs) heterostructures has drawn tremendous attention due to their unique and exotic optoelectronic properties. Coupling the IEs into optical cavities provides distinctive electromagnetic environments which plays an important role in controlling multiple optical processes such as optical nonlinear generation or photoluminescence enhancement. Here, the integration of IEs in TMDCs into plasmonic nanocavities based on a nanocube on a metallic mirror is reported. Spectroscopic studies reveal an order of magnitude enhancement of the IE at room temperature and a 5-time enhancement in fluorescence at cryogenic temperatures. Cavity modeling reveals that the enhancement of the emission is attributed to both increased excitation efficiency and Purcell effect from the cavity. The results show a novel method to control the excitonic processes in TMDC heterostructures to build high performance photonics and optoelectronics devices.

Photon-state transformations are the cornerstone of quantum optics. Recently a universal method to treat non-unitary transformations has been proposed [1] – [3] , based on singular value decomposition. In this work, we show an experimental demonstration of this approach with non-classical light, by studying the dynamics of photon pairs in a system of coupled waveguides.

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

We show a fabrication method based on ion implantation technique to create negatively charged boron vacancy centers in hexagonal boron nitride with optically addressable spin. Moreover, we elucidate additional optical properties of these defects.

Coherent excitation of quantum emitters in hexagonal boron nitride is inhibited by electron decay into intermediate dark states or spectral diffusion. We present an optical co-excitation scheme to reduce these transitions and amplify the photoluminescence.

Resonant excitation of solid-state quantum emitters enables coherent control of quantum states and generation of coherent single photons, which are required for scalable quantum photonics applications. However, these systems can often decay to one or more intermediate dark states or spectrally jump, resulting in the lack of photons on resonance. Here, we present an optical co-excitation scheme which uses a weak non-resonant laser to reduce transitions to a dark state and amplify the photoluminescence from quantum emitters in hexagonal boron nitride (hBN). Utilizing a two-laser repumping scheme, we achieve optically stable resonance fluorescence of hBN emitters and an overall increase of ON time by an order of magnitude compared to only resonant excitation. Our results are important for the deployment of atom-like defects in hBN as reliable building blocks for quantum photonic applications., Accepted to Physical Review Applied

Hexagonal boron nitride (hBN) is a layered dielectric material with a wide range of applications in optics and photonics. In this work, we demonstrate a fabrication method for few-layer hBN flakes with areas up to 5000 µ m 2 . We show that hBN in this form can be integrated with photonic microstructures: as an example, we use a circular Bragg grating (CBG). The layer quality of the exfoliated hBN flake on and off a CBG is confirmed by Raman spectroscopy and second-harmonic generation (SHG) microscopy. We show that the SHG signal is uniform across the hBN sample outside the CBG and is amplified in the center of the CBG.

Atomically thin monolayers of transition metal dichalcogenides (TMDs) have emerged as a promising class of novel materials for optoelectronics and nonlinear optics. However, the intrinsic nonlinearity of TMD monolayers is weak, limiting their functionalities for nonlinear optical processes such as frequency conversion. Here we boost the effective nonlinear susceptibility of a TMD monolayer by integrating it with a resonant dielectric metasurface that supports pronounced optical resonances with high quality factors: bound states in the continuum (BICs). We demonstrate that a WS

Integrating WS2 monolayers with resonant silicon metasurfaces hosting optical bound states in the continuum, we observe a strong increase of the second-harmonic intensity by a factor exceeding 1100.

Through the utilization of resonant dielectric metasurfaces governed by bound states in the continuum, we demonstrate a strong increase in the second-harmonic generation in WS2 monolayers by a factor exceeding 700

Quantum random number generation (QRNG) harnesses the intrinsic randomness of quantum mechanical phenomena. Here, we couple bright room-temperature single-photon emission from a hexagonal boron nitride atomic defect into a laser-written photonic chip and demonstrate QRNG. © 2020 The Author(s)

© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. In this work we couple bright room-Temperature single-photon emission from a hexagonal boron nitride atomic defect into a laser-written photonic chip. We perform single photon state manipulation with evanescently coupled waveguides acting as a multiple beam splitter, and generate a superposition state maintaining single photon purity. We demonstrate that such states can be utilized for quantum random number generation.

Quantum optical information systems offer the potential for secure communication and fast quantum computation. To fully characterise a quantum optical system one has to use quantum tomography.1 The integration of quantum optics onto photonic chips provides advantages such as miniaturisation and stability, significantly improving quantum tomography using both re-configurable, and more recently, simpler static designs. These on-chip designs have, so far, only used probabilistic single photon sources. Here we are working towards quantum tomography using a true deterministic source - an InGaAs quantum dot.

Quantum emitters in hexagonal boron nitride (hBN) are emerging as bright and robust sources of single photons for applications in quantum optics. In this work we present detailed studies on the limiting factors to achieve Fourier transform limited spectral lines. Specifically, we study phonon dephasing and spectral diffusion of quantum emitters in hBN via resonant excitation spectroscopy at cryogenic temperatures. We show that the linewidths of hBN quantum emitters are phonon broadened, even at 5 K, with typical values of the order of ∼ 1 G H z . While spectral diffusion dominates at increasing pump powers, it can be minimized by working well below saturation excitation power. Our results are important for future utilization of quantum emitters in hBN for quantum interference experiments.

Diamond resonators containing color-centers are highly sought after for application in quantum technologies. Bottom-up approaches are promising for the generation of single-crystal diamond structures with purposely introduced color centers. Here the possibility of using a polycrystalline diamond to grow single-crystal diamond structures by employing a pattern growth method is demonstrated. For, the possible mechanism of growing a single-crystal structure with predefined shape and size from a polycrystalline substrate by controlling the growth condition is clarified. Then, by introducing germanium impurities during the growth, localized and enhanced emission from fabricated pyramid shaped single-crystal diamonds containing germanium vacancy (GeV) color centers is demonstrated. Finally, linewidth of ∼500 MHz at 4 K from a single GeV center in the pyramid shaped diamonds is measured. The method is an important step toward fabrication of 3D structures for integrated diamond photonics.

Photonic cavities are valued in current research owing to the multitude of linear and nonlinear effects arising from densely confined light. Cavity designs consisting of low loss dielectric materials can achieve significant light confinement. Until now, the basic concepts in all-dielectric photonics such as anapole resonances have been primarily studied in high index materials. Here, we use photonic simulation to propose fabricable designs for higher confinement in low index dielectric cavities by incorporating the extensively studied isolated dielectric nanodisk into broader host structures. We further discuss on hexagonal boron nitride nanodisks for their potential use in quantum and nanophotonics applications.

Quantum random number generation (QRNG) harnesses the intrinsic randomness of quantum mechanical phenomena. On-chip photonic circuitry provides a robust and versatile platform that can address and explore fundamental questions in quantum as well as classical physics. Likewise, integrated waveguide-based architectures hold the potential for intrinsically scalable, efficient and compact implementations of photonic QRNG. Here, we harness the quantum emission from the two-dimensional material hexagonal boron nitride an emerging atomically thin medium that can generate single photons on demand while operating at room temperature. By means of a customized splitter arrangement, we achieve true random number generation through the measurement of single photons exiting one of four designated output ports, and subsequently verify the randomness of the sequences in accordance with the National Institute of Standards and Technology benchmark suite. Our results clearly demonstrate the viability and efficiency of this approach to on-chip deterministic random number generators.

Thermoelectric (TE) materials are increasingly promising for power generation in medium to high-temperature environments. Recent research on thermoelectric generators (TEGs) has determined the thermodynamic properties which impact the total efficiency and figure of merit (ZT) of these materials. A large Seebeck coefficient, high electrical conductivity and low thermal conductivity optimise ZT. This meta-study investigates silicides for potential TEG applications due to their high chemical stability and higher natural abundance than other TE materials. Data on the thermoelectric properties of CrSi2, FeSi2, Mg2Si and MnSi2, with a range of dopants, was sourced from a wide scope of literature and is analysed. The above thermodynamic properties contributing to ZT for each of these materials are graphed between 300 and 1000 K. It was found that chromium silicides are most effective at a temperature range of 600-800 K, and undoped magnesium silicides are most effective around 900 K. Oxide addition to β-FeSi2 produced relatively high ZT scores (ZT ≈ 0.5) among iron silicides. Rhenium substitution in manganese silicides produced a maximum figure of merit (1.05) at 900 K. Supersaturation via liquid quenching was determined to maintain high rhenium substitution and this technique may be the key to further improving the thermoelectric properties of other silicides.

© 2018 SPIE. Here we present our recent developments in temperature dependent ellipsometry, FTIR and emittance measurements of flat and structured vanadium dioxide (VO2) surfaces allowing significant control of switchable radiative cooling beyond that attainable via traditional VO2 surfaces. VO2 undergoes a metal-insulator transition at a critical temperature of ∼ 68°C; previous work has investigated tuning of this critical temperature over a wide range of temperatures. Here we exploit the shift in optical properties to produce surfaces with various emittance temperature profiles that modulate the thermal radiative transfer to/from a surface. Designing surfaces with different temperature emittance profiles requires accurate optical/thermal characterisation of materials. VO2 is produced by sputtering of vanadium followed by post deposition annealing in a 0.1Torr to 0.3Torr Air atmosphere at 450°C to 550°C, in-situ optical monitoring allows for accurate termination of the annealing process once the desired optical response is achieved.

The metabolism of glycosphingolipids by the malaria-causing parasite Plasmodium falciparum plays an important role in the progression of the disease. We report a new and highly sensitive method to monitor the uptake of glycosphingolipids in infected red blood cells (iRBCs). A tetramethylrhodamine-labeled glycosphingolipid (GM1-TMR) was used as a substrate. Uptake was demonstrated by fluorescence microscopy. The iRBCs were lysed with a 15% solution of saponin and washed with phosphate buffered saline to release intact parasites. The parasites were further lysed and the resulting homogenates were analyzed by capillary electrophoresis with laser-induced fluorescence detection. The lysate from erythrocytes infected at 1% parasitemia generated a signal twenty standard deviations larger than uninfected erythrocytes, which suggests that relatively low infection levels can be studied with this technique.

Experiments were conducted during 2004 and 2005 in Virginia and North Carolina to evaluate large-seeded, Virginia market type peanut response to a nitrophenolic plant growth regulator applied at 0.37 to 1.46 L/ha to peanut 45-60 DAP. Pod yield, percent extra large kernels (%ELK), percent total sound mature kernels (%TSMK), and crude protein levels of seed were not affected by the nitrophenolic plant growth regulator regardless of experiment (location and year). These experiments were conducted under a range of environmental and edaphic conditions with four cultivars. These data indicate that there is no benefit of applying the nitrophenolic plant growth regulator to Virginia market type peanut.

Experiments were conducted from 2002 through 2004 in North Carolina and during 2004 in Virginia to determine peanut response to harpin protein applied in the formulated product Messenger® ...

An effective means of removing the short wave-length light from a beam containing infra-red radiation of all wave-lengths, uses an echelette grating as a simple mirror. Light of wave-lengths short compared to the grating space, is diffracted out of the beam into the dispersed spectra. Light of wave-lengths long compared to the grating space, can only go into the undispersed zero-order spectrum, which falls in the direction of normal reflection if the grating were a mirror. By the use of echelette gratings with high intensities in the dispersed spectra, large reductions in the amount of short wave-length light in the central image can be effected. The wave-length at which most of the light changes from normal reflection into the beam to diffraction out of it, may be quite sharp, so that the effective filtering action may vary by a factor as large as four in a two-micron interval. When such a grating is substituted for a plane mirror in the illuminating system of an infra-red spectrometer, the scattered light in the monochromator is reduced by a factor of ten.

In a series of 129 patients having coronary angioplasties in St. James's Hospital in 1989, the average age was 54.8 (30-77 years). There were 102 (79%) men and 27 (21%) females. Clinical indications were unstable angina 62, stable angina 26, post myocardial infarction 39 and asymptomatic ischaemia 2. The distribution of coronary disease was single vessel 62%, double vessel 28%, triple vessel 7% and previous coronary bypass surgery 3%. Only 10 patients had more than one vessel dilated. Primary success was achieved in 119 (92%), there were no deaths, 3 patients had abrupt closure of the vessel during angioplasty and sustained a nonfatal myocardial infarction, 1 patient required urgent bypass surgery and 2 patients had peripheral vascular complications requiring surgery. There were 6 failed angioplasties, 4 of which had chronic total occlusion. At a mean follow-up of 5.3 months, 85 patients had no symptoms, 34 had angina, 2 developed myocardial infarction and 1 died suddenly at 5 months. Repeat angiography was performed in 96 (79%) patients. At follow-up, no symptoms were present in 69% of those with single vessel disease and 70% of multivessel disease. Of those who had more than one vessel dilated in multivessel disease, 80% were asymptomatic (P = NS). There were 11 patients with initial total occlusion at presentation, 4 had failed angioplasties, 5 recurrent angina of which 4 reoccluded and 1 restenosed and only 2 were asymptomatic and without restenosis. Angioplasty was performed with primary success (92%) and follow up results (70% asymptomatic). Those with single or multivessel disease had similar clinical outcome, favouring the use of target vessel angioplasty. Long term results following angioplasty of chronic total occlusions were poor and suggests the need for additional treatment.

Haploid cells of Physarum flavicomum differentiating to dormant microcysts exhibited prominent Golgi bodies, lysosomes, and autophagic vacuoles digesting intracellular materials. Total intracellular acid proteinase activities, as well as enzyme specific activity, increased during the encystment process. Lysosomes, isolated by fractionation of cell extracts on sucrose density gradients, were identified by their ultrastructural characteristics as well as their content of the following enzymes of high specific activity: acid proteinase, acid β-galactosidase, acid phosphatase, and β-glucuronidase. The lysosomal acid proteinase was chromatographically purified, and its molecular weight was estimated to be 32 000. The proteinase was most stable in the pH range of 2–3 which similarly corresponds to its pH optimum using hemoglobin and Azocasein, respectively, as substrates. Its isoelectric point was about 2. The enzyme exhibited little activity and was unstable at pH 7 and above. The rate of activity of the proteinase was maximal at 55 °C, and good stability of the enzyme was noted up to 45 °C. The proteinase required a thiol reagent for stability. Pepstatin, which specifically affects acid proteinases, inhibited the enzyme. Also, compounds reactive with enzyme thiol groups were highly effective inhibitors of the proteinase. The lysosomal enzyme is an acid (carboxyl) proteinase with essential thiol groups.

The effect of various purines, pyrimidines and nucleosides on the encystment of haploid cells ofPhysarum flavicomum was determined. Of the compounds tested guanine, guanosine, cytidine, cytosine, 5-methylcytosine and uracil had no effect on encystment. Adenosine, thymine, uridine and 3-methyladenine only slightly delayed encystment and protein degradation. Adenine and, to a lesser extent, hypoxanthine produced a significant inhibition of encystment and greatly increased rates of autolytic protein and RNA degradation, which eventually led to about 75% cell death in the adenine-exposed cells. The inhibition of microcyst formation by adenine was concentration dependent. The incubation of cells with adenine resulted initially in elevated intracellular levels of S-adenosylmethionine up to 3.5 times the level of untreated control cells.

Egypt during 1952–1960 achieved a more rapid and proportionately larger improvement in potable water supply for its rural population than any other developing country. The way in which this was done laid the groundwork for later difficulties in maintenance and extension of services. Similar problems arose in the Fayoum project in 1953–1964. A program for basic village services initiated in 1979 applied some of the lessons learned in the earlierprogram, but raised new environmental issues. The early change in water service was not followed by striking reductions in prevalence of childhood disease.

Understanding the behavior patterns of women in rural households regarding water and sanitation may be the key to solving the problem of why improvements in facilities may not be accompanied by a reduction in disease prevalence. An interdisciplinary team surveyed 312 households in two Egyp tian delta villages, examining46 of them in depth, with participant observation. Their patterns of storing water, and its use for drinking, cooking, washing, animal rearing and waste disposal are rooted in the woman's beliefs regarding cleanliness and what enhances the health and well-being of herfamily The local environment of surface and groundwater availability, quality andavailable drainage affect her choices. Otherfactors include local government institutions, available technology, information and educational facilities. time and energy expended on various practices, and social values held by the women and the community The women suggest practical solutions for their water and sanitation problems such as c...

Free CN radicals are formed from cyanogen at high temperature. Their absorption spectrum was observed in a furnace at 1500°K. From the lower limit of the absolute absorption coefficient found in Part I of this paper, their partial pressure and hence the equilibrium constant of the dissociation of cyanogen to free radicals are calculated. A lower limit for the heat of the reaction C2N2→2CN K1500∘K=1.1×10−12 H0=138.1(±1) kcal. follows directly. f=0.1 is estimated to be the most probable f value for the 2Σ→2Σ transition of CN. The most probable value of the heat of dissociation of cyanogen is calculated from this to be H0=146(±4) kcal. By calculating the partial pressure of CN at about 400°C, the thermal polymerization of cyanogen is explained as the addition of the free radicals formed to cyanogen molecules. From thermodynamic cycles, it is shown that the most probable value of the heat of dissociation of CO is 11.054 volts, and of the heat of vaporization of graphite 169.2 kcal., although 9.797 volts and...

Free CN radicals in the gaseous state are formed in the electric discharge through cyanogen. By the use of a very intense low pressure spark as a background the 0,0 and 1,1 bands of the 2Σ→2Σ transition of CN have been observed in absorption at short intervals of time after the end of this discharge. The intensities of the lines of the bands were measured by means of microphotometer traces of the spectra and of the characteristic curve of the photographic plate. They were corrected for the incomplete resolution of the spectrograph. Relative concentrations of CN were calculated from the sums of the intensities of the lines. The rate of disappearance of CN after the end of the discharge was studied and found to be the same over a large range of pressure and dilution with argon. A mechanism is proposed to account for this. In all cases the disappearance was exponential with a mean half‐life of 11 milliseconds. The half‐life of the first excited vibration state was 3 milliseconds, during which time about 10,0...

The absorption spectrum of HS is obtained by passing repeated flashes from a source of continuous background through a discharge tube in which HS radicals are formed from ${\mathrm{H}}_{2}$S by pulses of radiofrequency current synchronized to precede immediately the flashes. The spectrograms obtained show only one band at 3237A. The rotational structure indicates that the ground state is an inverted $^{2}\ensuremath{\Pi}$, and the excited state a $^{2}\ensuremath{\Sigma}$. Because of the strong $\ensuremath{\Lambda}\ensuremath{\Sigma}$ coupling in the $^{2}\ensuremath{\Pi}$ state the doublet is wide, and since the Boltzmann factor greatly favors $^{2}\ensuremath{\Pi}_{\frac{3}{2}}$, only the strongest branch, ${Q}_{2}$, from the $^{2}\ensuremath{\Pi}_{\frac{1}{2}}$ state is found. From $^{2}\ensuremath{\Pi}_{\frac{3}{2}}$ the $^{Q}P_{21}$ and $^{R}Q_{21}$ satellite branches as well as ${P}_{1}$, ${Q}_{1}$ and ${R}_{1}$ are found. For the $^{2}\ensuremath{\Pi}$ ground state the best values of the constants obtained are $B_{0}^{\ensuremath{'}\ensuremath{'}}=9.47$; $D_{0}^{\ensuremath{'}\ensuremath{'}}=\ensuremath{-}0.001$ and $A=\ensuremath{-}378.6$ ${\mathrm{cm}}^{\ensuremath{-}1}$. The constants for the excited $^{2}\ensuremath{\Sigma}$ state are $B_{0}^{\ensuremath{'}}=8.30$; $D_{0}^{\ensuremath{'}}=\ensuremath{-}0.00078$, and $\ensuremath{\gamma}=0.32$ ${\mathrm{cm}}^{\ensuremath{-}1}$. The origin of the 0,0 band is at 30,659.1 ${\mathrm{cm}}^{\ensuremath{-}1}$.

A small infrared spectrometer has been built for general use in the chemical laboratory. Employing a rock salt prism with a 40‐ ×50‐mm base, it records the spectra of samples linearly in transmittance or absorbance vs wavelength on flat 8‐ ×23½‐inch charts. Its single set of scanning conditions covers the range from 2 to 16 microns in 16 minutes with a resolution of 3 to 4 cm−1 at 10 microns and scattered light of less than 1% at 15 microns.