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Topic: Alpha emission

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  Alpha decay - Wikipedia, the free encyclopedia
Alpha decay is a form of radioactive decay in which an atomic nucleus ejects an alpha particle and transforms into a nucleus with mass number 4 less and atomic number 2 less.
Note that an alpha particle is a helium nucleus, and that both mass number and atomic number are conserved.
Alpha decay can essentially be thought of as nuclear fission where the parent nucleus splits into two daughter nuclei.
en.wikipedia.org /wiki/Alpha_emission   (185 words)

 MSN Encarta - Radioactivity
Loss of an alpha particle by a nucleus results in the formation of a new nucleus, lighter than the original by four mass units (the masses of the neutron and of the proton are about one unit each).
The emission of gamma rays is a compensation by the atomic nucleus for the unstable state that follows alpha and beta processes in the nucleus.
Unlike alpha particles, however, beta particles are emitted at many different speeds, and beta emitters must be distinguished from one another through the existence of the characteristic maximum and average speeds of their beta particles.
ca.encarta.msn.com /encyclopedia_761569327/Radioactivity.html   (1816 words)

Alpha particle emission is modeled as a barrier penetration process.
The alpha particle is the nucleus of the helium atom and is the nucleus of highest stability.
Though the most massive and most energetic of radioactive emissions, the alpha particle is the shortest in range because of its strong interaction with matter.
hyperphysics.phy-astr.gsu.edu /hbase/nuclear/radact.html   (564 words)

 EPA - Alpha Particles (EPA's Radiation Protection Program: Understanding Radiation)   (Site not responding. Last check: 2007-10-21)
Alpha particles (symbol a) are a type of ionizing radiation ejected by the nuclei of some unstable atoms.
Alpha particles have a velocity in air of approximately one-twentieth the speed of light, depending upon the individual particle's energy.
Because alpha particles are not radioactive, once they have lost their energy, they pick up free electrons and become helium.
www.epa.gov /radiation/understand/alpha.htm   (1179 words)

 Chemical Sciences: Mechanisms of Nuclear Reactions
Alpha radiation is therefore damaging, but it is not penetrating; alpha radiation can bestopped by a sheet of paper, a short distance in air, or human skin.
Alpha sources are very dangerous if their contents are breathed or consumed, because then the decaying nuclei are within the body and, short-range or not, can be highly destructive of human tissue.
The emission of a beta particle has the effect of leaving the nuclear mass unchanged but increasing the nuclear charge by one, and so the element produced by beta decay is one column to the right in the periodic chart from the original element.
www.psigate.ac.uk /newsite/reference/plambeck/chem1/p05012.htm   (486 words)

 Supplemental Notes on Decay Paths (RCS)
Yb decays by alpha emission 79% of the time, and by positron emission or electron capture [which are experimentally difficult to distinguish] 21% of the time).
alpha emission is generally only found in isotopes far below and far to the right of the stable isotopes (this is not so always true, and in fact is only true for the elements with Z = about 70 to about 80, as shown).
Alpha emission in fact becomes quite rare for elements with less than 84 neutrons.
www.haverford.edu /chem/Scarrow/GenChem/nuclearchem/decaypaths.html   (345 words)

 Qual Outline
As a consequence, strong emission lines are expected to dominate the galaxy's SED, and for the record, this inference is relatively insensitive to the stellar initial mass function, since it's only the massive stars which produce the UV ionizing radiation which is ultimately responsible for the emission lines.
To the central emission we add an absorption component representing neutral gas surrounding the HII region which is expanding at the expansion velocity of the shell.
This is the expression we use, which is simply the emission in the line divided by the continuum as measured to the red side of the line, corrected for cosmological expansion.
astron.berkeley.edu /~sdawson/qual/outline_v1.html   (10806 words)

 alpha   (Site not responding. Last check: 2007-10-21)
Alpha decay is a radioactive process in which a particle with two neutrons and two protons is ejected from the nucleus of a radioactive atom.
Thus, when uranium-238 (which has a Z of 92) decays by alpha emission, thorium-234 is created (which has a Z of 90).
Typical alpha particles will travel no more than a few centimeters in air and are stopped by a sheet of paper.
www.physics.isu.edu /radinf/alpha.htm   (196 words)

 [No title]
Fluorine-18 radioactively decays by the emission of a positron.
Alpha particle production is the only route by which unstable nuclei can spontaneously decay.
Alpha particles are more massive than beta particles.
www.chem.purdue.edu /gchelp/116exams/nuclear.html   (2797 words)

 [No title]   (Site not responding. Last check: 2007-10-21)
Alpha EmissionThe emission of alpha radiation, which we now know is the emissionof an alpha particle or helium nucleus 4He, is one of the common pathwaysby which a radioactive isotope can decay to a stable isotope.The atomic number of the nucleus decreases by two and the atomic mass decreasesby four.
Gamma EmissionEmission of gamma radiation is the emission of very high-energy photons, not the emission of particles.Many alpha and beta emissions are accompanied by gamma emissionsbecause the nucleus loses excess energy through gamma radiation.
involves emission of two photons of gamma radiation, of different energies, in addition to the emission of the energetic alpha particle.
www.ualberta.ca /~jplambec/che/course/p05013.htm   (219 words)

 S88B Poster
While 3.29 um emission appears coincident with Br Gamma emission at the periphery (white), stronger 3.29 um emission is observed exterior to the Br Gamma emission, outlining the PDR.
We detect Br Gamma and Br Alpha emission in the vicinity of the 2.2 um emission peak.
The signal-to-noise ratio is approximately 10 for the 3.29 um emission and 3 for the 3.4 um emission.
astro.pas.rochester.edu /~jagoetz/S88B/Welcome.pre   (1352 words)

 Astro-ph for busy people   (Site not responding. Last check: 2007-10-21)
However, the strong CIII emission predicted by this model is not observed, and the observed broad CIII] emission must come from a lower-density BLR component and should be accompanied by broad Ly-alpha emission which is not observed.
The least unlikely explanation for this spectrum seems to be that any intrinsic broad Ly-alpha emission is removed by smooth NV absorption in the red wing of the Ly-alpha emission line and by smooth Ly-alpha absorption in the blue wing of the Ly-alpha emission line.
Emission from the rotational lines of H2 is difficult to detect, unless disk gas masses are substantial (>0.1 M_J).
www.camk.edu.pl /~gwar/astro-ph/2004.05.14.html   (6371 words)

 WHAM Science
Emission line studies of HVCs promises to provide many new clues about the nature of these elusive objects.
Emission from the WIM of this classic H II region line had only been detected in the Galactic plane (b = 0) prior to WHAM.
Since most of the H-Alpha emission we detect arises from hydrogen recombination, atomic physics is the only thing that dictates the ratio of H-Alpha to H-Beta emission from most ionized intersteller gases.
www.astro.wisc.edu /wham/science.html   (1263 words)

 Alpha, beta, and gamma radiation
Alpha without gamma--From inspection of the Chart of the Nuclides and various reports containing diagrams and tables of radionuclide transformations, it is apparent that alpha emitters that do not emit gamma radiation are not very plentiful.
Pu with the emission of a 6.25 MeV alpha particle and with a 90.0 percent yield to
percent yield, alpha is followed by some form of deexcitation from the 0.04 MeV state—I leave it to you and your friend to determine whether this qualifies as alpha and beta emission, and, if so, whether it is accompanied by a detectable level of gamma.
hps.org /publicinformation/ate/q386.html   (1171 words)

 Ultrafaint H-alpha Emission from Intergalactic...(1Sep94)
Their initial program was to search for faint H-alpha emission arising from surface photoionization of intergalactic 21-cm clouds, an approach that offers the most sensitive probe available of the metagalactic ionizing radiation field at the present epoch.
The emission measures seen in light grey in the inverse grey-scale image are approximately 0.1 cm^-6 pc, dark grey in the tidal tail between the H I tails corresponds to 0.3-0.5 cm^-6 pc; fl corresponds to emission measures of 0.9 cm^-6 pc.
The emission measures are too high to arise from metagalactic photoionization alone, since at such high levels, H-alpha would have been detected easily from the H I spurs and the Leo Ring.
www.noao.edu /noao/noaonews/sep94/art5.html   (1001 words)

 Rachel Baker's REU homepage (Summer 2004)
This research focuses on the emission nebula surrounding the well-known O9.5V star zeta Ophiuchi, a runaway main-sequence star that is rapidly moving.
The h-alpha emission in the entire northern sky was mapped over a two year period from November 1996 until 1998, and the full set of data (37,565 individual spectra) from the WHAM survey is made available to download at
The rings are converted to spectra by summing each ring azimuthally, where the longest wavelength of the emission corresponds to the center and the shortest wavelength corresponds to the outer most ring.
www.astro.wisc.edu /~baker   (2509 words)

 Atomic Absorption and Emission Spectra
Thus, emission spectra are produced by thin gases in which the atoms do not experience many collisions (because of the low density).
The emission lines correspond to photons of discrete energies that are emitted when excited atomic states in the gas make transitions back to lower-lying levels.
Emission or absorption processes in hydrogen give rise to series, which are sequences of lines corresponding to atomic transitions, each ending or beginning with the same atomic state in hydrogen.
csep10.phys.utk.edu /astr162/lect/light/absorption.html   (408 words)

 NCA 110.01 - G. Mouze and R. A. Ricci: Alpha-particle emission in...   (Site not responding. Last check: 2007-10-21)
Emission of other light charged particles (LCP) in fission was later reported too, and ternary (or LCP accompanied) fission has been extensively studied.
This effect is clearly present for the alphas emitted in the direction of the light fragment, but can still be detected for the alphas emitted in the direction of the heavy fragment.
The direction of emission of the polar alphas is that of the electrostatic E field of the proton shells vibrating in the direction of the fission axis, whereas the direction of the emission of the equatorial alphas corresponds to the electromagnetic E field of these vibrating proton shells.
www.sif.it /cimento/toca/110.01/05/05.html   (2209 words)

 The Process of Alpha-Ray Emission (from radioactivity) --  Britannica Student Encyclopedia
The emission of an alpha particle is a drastic radioactive change.
It may be that the emission consists of a helium nucleus instead of one or more protons, because protons and neutrons tend to group themselves firmly in this way, even in a nucleus.
Because alpha particles have two positive charges and a mass of four units, their emission from nuclei produces daughter nuclei having a positive nuclear charge or atomic number two units less than their parents and a mass of four...
www.britannica.com /ebi/article-207141?tocId=207141   (918 words)

 Lyman Alpha Forest   (Site not responding. Last check: 2007-10-21)
There are clouds of gas between distant quasars and the Earth that absorb ultraviolet light at the wavelength of the Lyman alpha line of hydrogen at a wavelength of 122 nm.
Note that if Arp were correct and quasars had a redshift much larger than the redshift due to their distance, then there should be a gap on the blue side of the Lyman alpha emission line before the absorption lines began.
So if Arp were correct the Lyman alpha forest would have to be an intrinsic property of the quasar, which would be a very unlikely situation.
www.astro.ucla.edu /~wright/Lyman-alpha-forest.html   (390 words)

 Energy Crisis in Be star Radiation Emission?
In the first publication we have calculated the energy in the H-alpha emission due to the absorption of Lyman and Balmer continua from the Be stars, and compared the results with observations.
It is seen from Table 2 that the infrared emission calculated from the absorption of the Lyman continuum is inadequate to account for the observed infrared emission from Be stars of spectral types of B1 and later.
The suggestion that the ionizing photons to account for the infrared and H-alpha emissions come from a compact object implies that all the Be stars, at least the later spectral types, are binaries.
www.astro.virginia.edu /~dam3ma/benews/volume33/apparao.html   (1268 words)

 Untitled Document
Imaging through narrow band hydrogen alpha filters can bring remarkable enhancement to objects with singular or dominant emission in the hydrogen-alpha line.
These objects are mostly red emission nebulas but can also be complex nebulas with a dominant hydrogen-alpha emission component.
Many imagers are content with monochrome display of these images but some may desire to go further and create a color image using the hydrogen alpha data.
www.robgendlerastropics.com /HARGB.html   (1071 words)

 Nuclear Chemistry
The large mass nuclei tend to use alpha emission because it is a quick way for a large mass atom to lose a lot of nucleons.
As a result of the addition of the proton, the atomic number of an element increases during beta emission.
Gamma Emission occurs primarily after the emission of a decay particle.
www.bcpl.net /~kdrews/nuclearchem/nuclear.html   (680 words)

 Five Barrier Tunneling Model for Alpha Particle Halflife
A number of parameters must be calculated to model the barrier penetration which leads to alpha emission.
The nuclear influence is assumed to stop sharply when the emitted alpha and the reduced nucleus are just touching each other.
In addition to the tunneling probability calculated below, the alpha emission rate depends upon how many times an alpha particle with this energy inside the nucleus will hit the walls.
hyperphysics.phy-astr.gsu.edu /hbase/nuclear/alpdet2.html   (312 words)

Therefore, if a single alpha particle of sufficient energy were released at a point on the surface of a sheet of photographic film, a light linear smear with a dense spot toward the end of its path would be seen on the developed film.
When several alpha particles are emitted in all directions from the same source, therefore, the dense spots form a ring.
When an atom decays by alpha emission, as the alpha particle shoots out, there is a small amount of recoil by the atom (just as when a bullet fires, the gun rebounds in the other direction).
www.evolution-facts.org /Ev-V1/1evlch05a.htm   (11786 words)

 SN 1992ad: circumstellar H-alpha emission
We report the probable detection of narrow circumstellar H-alpha emission associated with the normal Type II supernova SN 1992ad at ~210 d after explosion.
There's H II region emission adjacent to the supernova, but the H-alpha from the supernova position is narrower than the H II region emission, and slightly blueshifted relative to it.
The change in velocity and width of the H-alpha emission at the supernova position lead us to believe that what we're seeing here is narrow emission associated with the supernova.
www.astro.su.se /~robert/92ad   (470 words)

 Title page for ETD etd-051199-154038
It was found that a correlation exists between the H-alpha intensity and infrared emission by dust grains in all four IRAS waveband images in the suspected scattering region of the Rosette Nebula.
A radial comparison between [SII] images and H-alpha images in the region of high polarization showed that the H-alpha intensity in that region is dominated by scattered H-alpha light from the Rosette Nebula.
A spatial comparison of the 12 m emission with the degree of polarization strongly suggested that multiple scattering is important in describing the observed radial behavior of polarization.
scholar.lib.vt.edu /theses/available/etd-051199-154038   (578 words)

 APOD: August 28, 1998 - Hydrogen Trifid   (Site not responding. Last check: 2007-10-21)
At visible wavelengths, the strongest emission line in this pattern is in the red part of the spectrum and is known as "Hydrogen-alpha" or just H-alpha.
This image of the nebula was taken using a filter to select only light near the H-alpha wavelength.
The relative strength of this emission can trace the densities of atoms within the gas cloud.
antwrp.gsfc.nasa.gov /apod/ap980828.html   (144 words)

 Observations of a complete sample of H{alpha} emission-line galaxies. Long-slit spectroscopy of galaxies in UCM lists 1 ...
Gray-scale images of the CCD spectra near the main emission lines, spatial profiles at the continuum and the line for [OIII]{lambda}5007 and H{alpha} lines, as well as plots of the coadded spectra of selected galaxies are presented, and a number of peculiar objects are described.
Line fluxes are relative to Hbeta=100 for all emission lines detected.
In case of no Hbeta line apparent, the fluxes are given relatives to Halpha=100.
www.cs.wisc.edu /niagara/data/nasa/A+AS_120_323.xml   (803 words)

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