HOME  TheInfoList.com 
NMR NUCLEAR MAGNETIC RESONANCE (NMR) is a physical phenomenon in which nuclei in a magnetic field absorb and reemit electromagnetic radiation . This energy is at a specific resonance frequency which depends on the strength of the magnetic field and the magnetic properties of the isotope of the atoms; in practical applications, the frequency is similar to VHF and UHF UHF television broadcasts (60–1000 MHz). NMR allows the observation of specific quantum mechanical magnetic properties of the atomic nucleus . Many scientific techniques exploit NMR phenomena to study molecular physics , crystals , and noncrystalline materials through nuclear magnetic resonance spectroscopy . NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging (MRI) [...More...]  "NMR" on: Wikipedia Yahoo 

Angular Momentum In physics , ANGULAR MOMENTUM (rarely, MOMENT OF MOMENTUM or ROTATIONAL MOMENTUM) is the rotational analog of linear momentum . It is an important quantity in physics because it is a conserved quantity – the angular momentum of a system remains constant unless acted on by an external torque . The definition of angular momentum for a point particle is a pseudovector R×P, the cross product of the particle's position vector R (relative to some origin) and its momentum vector P = mV. This definition can be applied to each point in continua like solids or fluids, or physical fields . Unlike momentum, angular momentum does depend on where the origin is chosen, since the particle's position is measured from it [...More...]  "Angular Momentum" on: Wikipedia Yahoo 

Xenon129 Naturally occurring XENON (54XE) is made of eight stable isotopes and one very longlived isotope. (124Xe, 126Xe, and 134Xe are predicted to undergo double beta decay , but this has never been observed in these isotopes, so they are considered to be stable.) Xenon has the second highest number of stable isotopes . Only tin , with 10 stable isotopes, has more. Beyond these stable forms, there are over 30 unstable isotopes and isomers that have been studied, the longestlived of which is 136Xe, which undergoes double beta decay with a halflife of 2.165 ± 0.016(stat) ± 0.059(sys) ×1021 years with the next longest lived being 127Xe with a halflife of 36.345 days. Of known isomers, the longestlived is 131mXe with a halflife of 11.934 days. 129Xe is produced by beta decay of 129I (halflife : 16 million years); 131mXe, 133Xe, 133mXe, and 135Xe are some of the fission products of both 235U and 239Pu , and therefore used as indicators of nuclear explosions [...More...]  "Xenon129" on: Wikipedia Yahoo 

Neutrons 5000000000000000000♠0 e 3021799999999999999♠(−2±8)×10−22 e (experimental limits) ELECTRIC DIPOLE MOMENT < 6974290000000000000♠2.9×10−26 e⋅cm (experimental upper limit) ELECTRIC POLARIZABILITY 6997116000000000000♠1.16(15)×10−3 fm3 MAGNETIC MOMENT 3026033763500000000♠−0.96623650(23)×10−26 J ·T −1 3002895812437000000♠−1.04187563(25)×10−3 μB 2999808695726999999♠−1.91304273(45) μN MAGNETIC POLARIZABILITY 6996370000000000000♠3.7(20)×10−4 fm3 SPIN 1/2 ISOSPIN −1/2 PARITY +1 CONDENSED I (J P ) = 1/2(1/2+)The NEUTRON is a subatomic particle , symbol n or n0 , with no net electric charge and a mass slightly larger than that of a proton . Protons and neutrons, each with mass approximately one atomic mass unit , constitute the nucleus of an atom , and they are collectively referred to as nucleons . Their properties and interactions are described by nuclear physics [...More...]  "Neutrons" on: Wikipedia Yahoo 

Platinum195 Natural PLATINUM (78Pt) occurs in six stable isotopes (192Pt, 194Pt, 195Pt, 196Pt, 198Pt) and one very longlived (halflife 6.50×1011 years) radioisotope (190Pt). There are also 31 known artificial radioisotopes, the longestlived of which is 193Pt with a halflife of 50 years. All other isotopes have halflives under a year, most under a day [...More...]  "Platinum195" on: Wikipedia Yahoo 

Perpendicular In elementary geometry , the property of being PERPENDICULAR (PERPENDICULARITY) is the relationship between two lines which meet at a right angle (90 degrees ). The property extends to other related geometric objects . A line is said to be perpendicular to another line if the two lines intersect at a right angle. Explicitly, a first line is perpendicular to a second line if (1) the two lines meet; and (2) at the point of intersection the straight angle on one side of the first line is cut by the second line into two congruent angles . Perpendicularity can be shown to be symmetric , meaning if a first line is perpendicular to a second line, then the second line is also perpendicular to the first. For this reason, we may speak of two lines as being perpendicular (to each other) without specifying an order. Perpendicularity easily extends to segments and rays [...More...]  "Perpendicular" on: Wikipedia Yahoo 

Gradient In mathematics , the GRADIENT is a multivariable generalization of the derivative . While a derivative can be defined on functions of a single variable, for functions of several variables , the gradient takes its place. The gradient is a vectorvalued function , as opposed to a derivative, which is scalarvalued . Like the derivative, the gradient represents the slope of the tangent of the graph of the function . More precisely, the gradient points in the direction of the greatest rate of increase of the function, and its magnitude is the slope of the graph in that direction. The components of the gradient in coordinates are the coefficients of the variables in the equation of the tangent space to the graph. This characterizing property of the gradient allows it to be defined independently of a choice of coordinate system, as a vector field whose components in a coordinate system will transform when going from one coordinate system to another [...More...]  "Gradient" on: Wikipedia Yahoo 

Nuclide A NUCLIDE (from nucleus ) is an atomic species characterized by the specific constitution of its nucleus, i.e., by its number of protons Z, its number of neutrons N, and its nuclear energy state . The word nuclide was proposed by Truman P. Kohman in 1947. Kohman originally suggested nuclide as referring to a "species of nucleus" defined by containing a certain number of neutrons and protons. The word thus was originally intended to focus on the nucleus. CONTENTS * 1 Nuclides vs isotopes * 2 Nuclides and isotopes * 3 Origins of naturally occurring nuclides * 4 Artificially produced nuclides * 5 Summary table for numbers of each class of nuclides * 6 Nuclear properties and stability * 6.1 Even and odd nucleon numbers * 7 See also * 8 References * 9 External links NUCLIDES VS ISOTOPES Nuclide Nuclide refers to a nucleus rather than to an atom [...More...]  "Nuclide" on: Wikipedia Yahoo 

Cadmium113 Naturally occurring CADMIUM (48Cd) is composed of 8 isotopes . For two of them, natural radioactivity was observed, and three others are predicted to be radioactive but their decays were never observed, due to extremely long halflife times. The two natural radioactive isotopes are 113Cd (beta decay , halflife is 8.04 × 1015 years) and 116Cd (twoneutrino double beta decay , halflife is 2.8 × 1019 years). The other three are 106Cd, 108Cd (double electron capture ), and 114Cd (double beta decay); only lower limits on their halflife times have been set. At least three isotopes—110Cd, 111Cd, and 112Cd—are absolutely stable (except, theoretically, to spontaneous fission ). Among the isotopes absent in the natural cadmium, the most longlived are 109Cd with a halflife of 462.6 days, and 115Cd with a halflife of 53.46 hours [...More...]  "Cadmium113" on: Wikipedia Yahoo 

Silicon29 SILICON (14Si) has 25 known isotopes , with mass numbers ranging from 22 to 45. 28Si (the most abundant isotope, at 92.23%), 29Si (4.67%), and 30Si (3.1%) are stable. The longestlived radioisotope is 32Si, which is produced by cosmic ray spallation of argon . Its halflife has been determined to be approximately 150 years (0.21 MeV), and it decays by beta emission to 32P (which has a 14.28 day halflife ) and then to 32S . After 32Si, 31Si has the second longest halflife at 157.3 minutes. All others have halflives under 7 seconds. The least stable is usually 43Si with a halflife greater than 60 nanoseconds. A chart showing the relative abundances of the naturally occurring isotopes of Silicon [...More...]  "Silicon29" on: Wikipedia Yahoo 

Boron11 BORON (5B) naturally occurs as isotopes 10B and 11B, the latter of which makes up about 80% of natural boron. There are 14 radioisotopes that have been discovered, with mass numbers from 6 to 21, all with short halflives , the longest being that of 8B, with a halflife of only 770 milliseconds (ms) and 12B with a halflife of 20.2 ms. All other isotopes have halflives shorter than 17.35 ms, with the least stable isotope being 7B, with a halflife of 150 yoctoseconds (ys). Those isotopes with mass below 10 decay into helium (via shortlived isotopes of beryllium for 7B and 9B) while those with mass above 11 mostly become carbon . 12B has molecular form with an icosahedral structure. A chart showing the abundances of the naturally occurring isotopes of boron [...More...]  "Boron11" on: Wikipedia Yahoo 

Phosphorus31 Although PHOSPHORUS (15P) has 23 ISOTOPES from 24P to 46P, only one of these isotopes is stable 31P; as such, it is considered a monoisotopic element. The longestlived radioactive isotopes are 33P with a halflife of 25.34 days and 32P with a halflife of 14.263 days. All other have halflives under 2.5 minutes, most under a second. The least stable is 25P with a halflife shorter than 30 nanoseconds—the halflife of 24P is unknown. CONTENTS* 1 Radioactive isotopes * 1.1 Phosphorus32 * 1.2 Phosphorus33 * 2 List of isotopes * 2.1 Notes * 3 References * 4 External links RADIOACTIVE ISOTOPESPHOSPHORUS3232P , a beta emitter (1.71 MeV) with a halflife of 14.3 days, is used routinely in lifescience laboratories, primarily to produce radiolabeled DNA and RNA probe, e.g. for use in Northern blots or Southern blots [...More...]  "Phosphorus31" on: Wikipedia Yahoo 

Chlorine35 CHLORINE (17CL) has 24 isotopes with mass numbers ranging from 28Cl to 51Cl and 2 isomers (34mCl and 38mCl). There are two principal stable isotopes , 35Cl (75.78%) and 37Cl (24.22%), giving chlorine a standard atomic weight of 35.45. The longestlived radioactive isotope is 36Cl, which has a halflife of 301,000 years. All other isotopes have halflives under 1 hour, many less than one second. The shortestlived are 29Cl and 30Cl, with halflives less than 20 and 30 nanoseconds, respectively—the halflife of 28Cl is unknown. CONTENTS * 1 Chlorine36 (36Cl) * 2 List of isotopes * 2.1 Notes * 3 References * 4 External links CHLORINE36 (36CL) Main article: Chlorine36 Trace amounts of radioactive 36Cl exist in the environment, in a ratio of about 7×10−13 to 1 with stable isotopes. 36Cl is produced in the atmosphere by spallation of 36Ar by interactions with cosmic ray protons [...More...]  "Chlorine35" on: Wikipedia Yahoo 

Carbon13 CARBON13 (13C) is a natural, stable isotope of carbon with a nucleus containing six protons and seven neutrons . As one of the environmental isotopes , it makes up about 1.1% of all natural carbon on Earth. CONTENTS * 1 Detection by mass spectrometry * 2 Uses in science * 3 See also * 4 Notes DETECTION BY MASS SPECTROMETRYA mass spectrum of an organic compound will usually contain a small peak of one mass unit greater than the apparent molecular ion peak (M) of the whole molecule. This is known as the M+1 peak and comes from the handful of molecules that contain a 13C atom in place of a 12C. A molecule containing one carbon atom will be expected to have an M+1 peak of approximately 1.1% of the size of the M peak, as 1.1% of the molecules will have a 13C rather than a 12C [...More...]  "Carbon13" on: Wikipedia Yahoo 

Spectral Resolution The SPECTRAL RESOLUTION of a spectrograph , or, more generally, of a frequency spectrum , is a measure of its ability to resolve features in the electromagnetic spectrum . It is usually denoted by {displaystyle Delta lambda } , and is closely related to the RESOLVING POWER of the spectrograph, defined as R = {displaystyle R={lambda over Delta lambda }} , where {displaystyle Delta lambda } is the smallest difference in wavelengths that can be distinguished at a wavelength of {displaystyle lambda } . For example, the Space Telescope Imaging Spectrograph Spectrograph (STIS) can distinguish features 0.17 nm apart at a wavelength of 1000 nm, giving it a resolution of 0.17 nm and a resolving power of about 5,900 [...More...]  "Spectral Resolution" on: Wikipedia Yahoo 

Molecular Physics MOLECULAR PHYSICS is the study of the physical properties of molecules , the chemical bonds between atoms as well as the molecular dynamics . Its most important experimental techniques are the various types of spectroscopy ; scattering is also used. The field is closely related to atomic physics and overlaps greatly with theoretical chemistry , physical chemistry and chemical physics . In addition to the electronic excitation states which are known from atoms, molecules exhibit rotational and vibrational modes whose energy levels are quantized. The smallest energy differences exist between different rotational states: pure rotational spectra are in the far infrared region (about 30  150 µm wavelength ) of the electromagnetic spectrum . Vibrational spectra are in the near infrared (about 1  5 µm) and spectra resulting from electronic transitions are mostly in the visible and ultraviolet regions [...More...]  "Molecular Physics" on: Wikipedia Yahoo 