Substances consisting of larger, nonpolar molecules have larger attractive forces and melt at higher temperatures. Molecular solids composed of molecules with permanent dipole moments polar molecules melt at still higher temperatures.
A crystalline solid, like those listed in Table 7 , has a precise melting temperature because each atom or molecule of the same type is held in place with the same forces or energy. Thus, the attractions between the units that make up the crystal all have the same strength and all require the same amount of energy to be broken. The gradual softening of an amorphous material differs dramatically from the distinct melting of a crystalline solid. This results from the structural nonequivalence of the molecules in the amorphous solid.
Some forces are weaker than others, and when an amorphous material is heated, the weakest intermolecular attractions break first. As the temperature is increased further, the stronger attractions are broken.
Thus amorphous materials soften over a range of temperatures. Carbon is an essential element in our world. The unique properties of carbon atoms allow the existence of carbon-based life forms such as ourselves. Carbon forms a huge variety of substances that we use on a daily basis, including those shown in Figure 7. You may be familiar with diamond and graphite, the two most common allotropes of carbon. Allotropes are different structural forms of the same element.
Diamond is one of the hardest-known substances, whereas graphite is soft enough to be used as pencil lead. These very different properties stem from the different arrangements of the carbon atoms in the different allotropes. You may be less familiar with a recently discovered form of carbon: graphene. Graphene was first isolated in by using tape to peel off thinner and thinner layers from graphite. It is essentially a single sheet one atom thick of graphite.
Graphene, illustrated in Figure 8 , is not only strong and lightweight, but it is also an excellent conductor of electricity and heat. These properties may prove very useful in a wide range of applications, such as vastly improved computer chips and circuits, better batteries and solar cells, and stronger and lighter structural materials.
In a crystalline solid, the atoms, ions, or molecules are arranged in a definite repeating pattern, but occasional defects may occur in the pattern. Several types of defects are known, as illustrated in Figure 9. Vacancies are defects that occur when positions that should contain atoms or ions are vacant. Less commonly, some atoms or ions in a crystal may occupy positions, called interstitial sites , located between the regular positions for atoms. Other distortions are found in impure crystals, as, for example, when the cations, anions, or molecules of the impurity are too large to fit into the regular positions without distorting the structure.
Trace amounts of impurities are sometimes added to a crystal a process known as doping in order to create defects in the structure that yield desirable changes in its properties. For example, silicon crystals are doped with varying amounts of different elements to yield suitable electrical properties for their use in the manufacture of semiconductors and computer chips. Some substances form crystalline solids consisting of particles in a very organized structure; others form amorphous noncrystalline solids with an internal structure that is not ordered.
The main types of crystalline solids are ionic solids, metallic solids, covalent network solids, and molecular solids. It is also found in Mars' atmosphere at 0. This noble gas can also be found down on Earth.
Some mineral springs emit xenon. Companies obtain the gas for commercial use from industrial plants that extract the gas from liquid air. Xenon may also be found in the Earth. For a long time, scientist suspected that 90 percent more of the gas should be found in the Earth's atmosphere, based on their knowledge of other noble gases.
Eventually, scientists, including Ma, found evidence that the missing gas may be found at the Earth's core. The extreme temperatures and pressures found in Earth's core may cause xenon to bond with iron and nickel located in the core, storing the gas there.
Xenon creates a blue or lavender glow when subjected to an electrical discharge. Lamps that use xenon illuminate better than conventional lights.
For example, stroboscopic lamps, photographic flash lamps, high-intensive arc-lamps for motion picture projection, some lamps used for deep-sea observation, bactericidal lamps, sunbed lamps and high-pressure arc all use this gas. In fact, you probably see xenon lamps on a regular basis.
Some vehicle headlights use xenon. If you see headlights that give off a soft blue glow, they are probably made with xenon. The gas has other uses, too. The other strong physics case for using solid xenon is searching for neutrinoless double beta decay. The possible non-vanishing Majorana mass component of neutrinos indicates the non-zero probability of having self-conjugate states of neutrinos, which means the neutrinos can be their own antiparticles.
Therefore, there is a small probability of a neutrino emitted from a nucleon through beta decay that can be absorbed into the other nucleon in the same nucleus; a mono-enegetic beta signal would thus be observed with no neutrinos carrying off momentum.
The Xe enriched solid phase volume, if phonon readout is demonstrated, is a superior detector for a neutrinoless double beta decay experiment due to substantially more quanta created through phonon channel, hence better energy resolution, compared to the ionization and scintillation channel.
Therefore, once the phonon signal readout is guaranteed, the solid phase is the best strategy of using the xenon for the neutrinoless double decay search. Navbar Toggle. Projects: Solid Xenon The solid crystalline phase of xenon inherits most of the advantages of using liquid xenon as a detector target material for low energy particles; transparency, self-shielding, absence of intrinsic background, and ionization drift.
Team Members Jong-Hee Yoo.
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