This noble gas is colorless and odorless. It has a full outer shell of electrons, rendering it largely inert to reactions with other elements. Unlike its fellow noble gas neon, however, krypton does make some compounds. The most common is the colorless solid krypton difluoride (KrF2), according to the Thomas Jefferson National Linear Accelerator Laboratory. Krypton difluoride is only stable below minus 22 degrees Fahrenheit (minus 30 degrees Celsius), according to Chemicool.
Because krypton is so rare (and thus expensive), it has limited use. The gas is injected into some incandescent lightbulbs, because it extends the life of the tungsten filament that makes those bulbs glow, according to Universal Industrial Gases Inc., a supplier of industrial gases production equipment and related services. Because it is such a heavy gas, krypton is also sealed between the glass of some double-paned windows to help them trap heat. But even for this purpose, the noble gas argon is usually used because it is cheaper, according to Universal Industrial Gases.
The Krypton
The discovery of krypton occurred partially by accident. Scottish chemist William Ramsay and English chemist Morris Travers were extracting argon for air in hopes of evaporating it and finding a lighter chemical element to fill the gap in the Periodic Table between argon and helium.
He and his colleagues have used a krypton isotope, krypton-81, with a half-life of 230,000 years to date ice cores in the Antarctic back to 120,000 years old. (The oldest Antarctic ice ever found fell as snow 800,000 years ago.) Bubbles in the ice trap atmospheric gases as they were when the snow fell, Buizert told Live Science. By measuring the levels of krypton-81 and comparing them to the current atmosphere, researchers can use the known rate of decay of the isotope to determine the ice's age.
Far from the glaciers of Antarctica, krypton-81 has also been used to date amazing old groundwater in the Sahara Desert. A 2004 study in the journal Geophysical Research Letters revealed that in certain areas of southwestern Egypt, the groundwater reaching the surface hasn't seen the light of day for 1 million years.
There has been a bewildering increase in the number and types of lasers available to the modern surgeon for the treatment of a variety of lesions. Pigmented and vascular lesions lend themselves to laser therapy and are common presentations in the cosmetic practice. While many different lasers may be effective for the treatment of these lesions, each has its own advantages and disadvantages. A detailed understanding of the specific properties and the applicability of the different lasers is vital if one is to successfully incorporate these lasers into one's practice. In this article, we discuss the different types of lasers available for the treatment of these lesions, discuss the specific indications and limitations and present our experience with the krypton laser.
For some reason, a lot of people want to know what the element krypton looks like. It turns out that you look at krypton every day, although you may not actually see it. Krypton is one of the gases that makes up the earth's atmosphere. Unfortunately for all of the krypton fans out there, there is very little krypton in the atmosphere. The earth's atmosphere is roughly 0.0001% krypton, or about one part per million.
Things become more interesting when an electric current is sent through a container of low pressure krypton. When this is done, krypton lights up in much the same way a fluorescent light bulb does and glows with a smokey-white light. This glowing gas is called a plasma. A plasma is a state of matter that is different than solids, liquids and gases, the more familiar states of matter. Although similar to gases, plasmas contain ions and free electrons. When one of the free electrons joins with one of the ions to form a neutral atom, energy is lost by the electron. This energy is usually emitted in the form of light. The color of the light depends on the amount of energy lost by the electron. Electrons that lose a little energy emit light towards the red end of the spectrum while electrons that lose a lot of energy emit light towards the blue end of the spectrum.
The exact spectrum emitted by a plasma depends on the available energy levels of the ions it is made of. Different elements produce different spectra when they are emitting light as a plasma. This is sort of like a fingerprint composed of light. Ever wonder how scientists know what the sun and other stars are made of? Scientists are able to match the patterns they see in an object's spectrum with the patterns produced by elements they have in their laboratories. So, if they see a pattern that matches krypton's, they know that there must be some krypton in that object.
We have developed a new method to measure krypton traces in xenon at unprecedented low concentrations. This is a mandatory task for many near-future low-background particle physics detectors. Our system separates krypton from xenon using cryogenic gas chromatography. The amount of krypton is then quantified using a mass spectrometer. We demonstrate that the system has achieved a detection limit of 8 ppq (parts per quadrillion) and present results of distilled xenon with krypton concentrations below 1 ppt.
The inert gas krypton with its unstable isotope \(^85\mathrmKr \) is one of the most serious internal background sources for LXe detectors used in low-background experiments. It is homogeneously distributed in the xenon and cannot be discriminated by shielding or fiducial volume cuts. \(^85\mathrmKr \) has a half life of 10.8 years and is an almost pure \(\beta ^-\) emitter (99.56 % branching ratio) with end-point energy of 687 keV [5]. The activity of the man-made isotope \(^85\mathrmKr \) in the atmosphere, produced in sizable quantities by nuclear fission and released by nuclear-fuel reprocessing plants and nuclear weapon tests, has been steadily increasing over time. The present-day activity concentration is approximately 1.4 Bq/m\(^3\) [6, 7], corresponding to a relative isotopic abundance of \(^85\mathrmKr \)/\(^\mathrmnat \mathrmKr \) of 2 \(\times 10^-11\) mol/mol [8].
The mass spectroscopic technique is used to quantify the abundance of natural krypton in given xenon gas batches down to the ppq regime. The setup can be separated into four parts: sample preparation, ion source, mass analyzer and detector. The ion source, mass analyzer and detector belong to a customized sector field mass spectrometer (Vacuum Generators model VG 3600) that is described in Sect. 2.1. The sample preparation, based upon cryogenic gas chromatography, is the essential new development and will be discussed in Sect. 2.2.
The mass spectrometer is a customized version of a VG 3600 (Fig. 1) capable of quantifying an amount of natural krypton of less than 10\(^-13\) cm\(^3\) STPFootnote 1 [14]. It is located at the Max-Planck-Institut für Kernphysik in Heidelberg, Germany.
The sample is collected by cryogenic pumping on a cold finger which contains a small amount of activated carbon, which is installed between the sample preparation part and ion source. When warming up the cold finger, the gaseous sample distributes in the entire volume of ion source, mass analyzer and detectors. Ionization, acceleration and focusing take place in the ion source of the mass spectrometer. Electrons are emitted from a hot filament and ionize the sample gas. The ions are accelerated and focused in electric fields. Their mass separation is achieved by a variable magnetic dipole-field. The ions are detected by a continuous dynode amplifier (SEM = secondary electron multiplier) counting events above a predefined threshold optimized for its signal/background ratio. In order to achieve the high sensitivity goals batch sizes on the order of 1 cm\(^3\) xenon gas are needed. However, this amount of xenon gas would result in a pressure much above the critical pressure of 10\(^-6\) mbar [15] in the spectrometer. Thus, the krypton must be separated from the bulk xenon before it is fed into the spectrometer. This separation is achieved by the gas chromatography system.
The krypton/xenon separation is performed via gas chromatography in the setup sketched in Fig. 2. The amount of helium carrier gas used in this process exceeds the size of the xenon batch by more than a factor of 50. Therefore, the purity specifications in terms of krypton inside the helium gas are strict. To reach sub-ppt sensitivity, the krypton concentration in the helium has to be at or below the ppq level. In this work grade 6.0 helium is purified using an adsorbent filled packed column T1 (10 mm inner diameter, 8.18 g Carbosieve S-III by Supelco Analytical) immersed in a liquid nitrogen bath. Pushed forward by the helium carrier, the gas mixture passes another adsorbent filled column T2 (6 mm inner diameter, 0.64 g Chromosorb 102 by Johns Manville) immersed in a coolant liquid (ethanol). Due to differences in the interaction strength of each constituent with the adsorbent, krypton and xenon can be separated if the flow of the carrier gas, the pressure gradients and the temperature are properly adjusted (see Fig. 3). The temperature of the ethanol coolant and the helium gas flow for the separation in this work were fixed to \(-\)80 \(^\circ \)C and 7 standard cubic centimetre per minute.
Signal of a thermal conductivity detector versus time for a krypton/xenon separation (0.5 cm\(^3\) krypton, 1.0 cm\(^3\) xenon) via cryogenic gas chromatography using an adsorbent filled packed column identical to T2 of the gas chromatographic system
The separated krypton is trapped in a third adsorbent filled packed column T3, identical to T2. By heating up T3 after the chromatographic process the krypton is released and can be transferred to the mass spectrometer by cryogenic pumping to the cold finger mounted next to the ion source of the mass spectrometer. 2ff7e9595c
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