What is Alpha particle: Definition and 135 Discussions

Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produced in other ways. Alpha particles are named after the first letter in the Greek alphabet, α. The symbol for the alpha particle is α or α2+. Because they are identical to helium nuclei, they are also sometimes written as He2+ or 42He2+ indicating a helium ion with a +2 charge (missing its two electrons). Once the ion gains electrons from its environment, the alpha particle becomes a normal (electrically neutral) helium atom 42He.
Alpha particles have a net spin of zero. Due to the mechanism of their production in standard alpha radioactive decay, alpha particles generally have a kinetic energy of about 5 MeV, and a velocity in the vicinity of 4% of the speed of light. (See discussion below for the limits of these figures in alpha decay.) They are a highly ionizing form of particle radiation, and (when resulting from radioactive alpha decay) usually have low penetration depth (stopped by a few centimeters of air, or by the skin).
However, so-called long range alpha particles from ternary fission are three times as energetic, and penetrate three times as far. The helium nuclei that form 10–12% of cosmic rays are also usually of much higher energy than those produced by nuclear decay processes, and thus may be highly penetrating and able to traverse the human body and also many meters of dense solid shielding, depending on their energy. To a lesser extent, this is also true of very high-energy helium nuclei produced by particle accelerators.

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  1. physadict

    Alpha particle energy in MCNP6

    15- mode a 16- m1 1000. -0.111894 $MAT1 17- 8000. -0.888106...
  2. J

    Alpha particle close to the nucleus

    Hello everyone, while studying I found this task in my textbook. Solving this problem with the help of the formula seems quite straightforward. But I get a different result than the solution the textbook offers. I get: Around ##5∗10^{−15}m## (which is a typical solution for a radius of a...
  3. freddie_mclair

    I What kind of energy is released in a nuclear fusion reaction?

    Hi, I have a fundamental (and maybe silly question) but I couldn't find a proper answer anywhere yet: For example, for a nuclear fusion reaction of Tritium (T) and Deuterium (D), we get an alpha particle (##\alpha##) a neutron (n) and energy release due to the mass difference ##\Delta...
  4. haha0p1

    Kinetic energy of an alpha particle

    Kindly help me solve this question. The only thing so far that I know in this question is that energy is conserved and the momentum of Alpha particle will equal momentum of Thorium.
  5. W

    I Can you tell the difference between two neutrons in an alpha particle?

    Can you tell the difference between two neutrons in an alpha particle? In one alpha particle, we know that the sum of the spins of two neutrons is zero. Can a neutron with upspin and a neutron with downspin be distinguished from each other? Or can't you tell because it's superimposed?
  6. W

    Determine how much energy the alpha particle carries

    I can follow through all of this worked example until the final step 55/56x4.84= 4.75MeV Where does the 56 come from?
  7. O

    I Maximum acceleration of an alpha particle?

    I would like to estimate the maximum acceleration (or deceleration) of an alpha particle that is backscattered by a heavy atom, like in Rutherford backscattering. I am interested in the order of magnitude, not in a precise value. I am assuming the collision is elastic. The kinetic energy of the...
  8. PandaKitten

    Estimating the energy of an alpha particle using Bethe's formula

    The question is below. I tried reasoning that because x is constant, E is also constant however that gives me values in the range of 10^51. Then I tried to use numpy's ivp_solve function to solve the differential equation however I wasn't able to get that working either. Apparently I'm meant to...
  9. C

    Rutherford Scattering of an Alpha Particle

    I have the equation but I am unsure of what my r min would be. Is it the sum of the radii or the difference? I am also confused on what z1 would be. I am fairly sure z2 is the atomic number of Fe(26) but I am unsure of this as well. Edit: I just read that z1 could be 2, is this correct?
  10. H

    B Alpha particle in a force field depiction

    Hello, I was glazing through what I would consider an advanced physics textbook and I saw this image. It is a schematic picture of an alpha-particle in a field of an atom. Now, can someone get me started on what (and why and how) is going on in it? Especially with the fraction with pi.
  11. F

    Why does an alpha particle curve less in a magnetic field than a beta?

    Suppose you are analyzing this image. The question to answer is: Explain why the alpha particle's path has a larger radius than either of the beta particle paths. Justify your answer using either momentum or charge-to-mass ratio. When you are answering this, suppose you know that , in...
  12. E

    Closest approach of alpha particle - two separate methods

    I've found two methods for doing this problem and they give different answers. Method 1: Assume the larger nucleus does not move, and simply equate energies before the collision and at the point of closest approach:$$\frac{1}{2} m v^{2} = \frac{qQ}{4\pi\epsilon_{0}r}$$ Method 2: Assume the...
  13. I

    Minimum separation between incoming proton and alpha particle

    Proton is going towards the ##\alpha## particle. So, I am thinking of using the conservation of energy as the initial kinetic energy of the proton is known and initial interaction potential energy is zero. But, we don't know the kinetic energies of proton and ##\alpha## particle when they are at...
  14. brotherbobby

    Alpha Particle Scattering and angular momentum

    Statement of the problem : "Using the definition L = r ##\times## p, prove that the direction of L is constant for an alpha (##\alpha##) particle whose scattering is shown in the diagram below. " Relevant equations : We are aware that the scattering takes place via a central force F = F(r)...
  15. S

    Rate of emission of alpha particle in uranium decay

    Homework Statement U - 238 is undergoing alpha emission into Th - 234. U - 238 has half – life of 109 years. Calculate the emission rate of alpha when uranium has mass of 10 grams Homework Equations A = λN A = A0 (1/2)n , n = t / half - life The Attempt at a Solution Not sure how to do it but...
  16. ezfzx

    I Reconciling alpha particle mass

    Ugh ... I remember there was a reason ... but forgot what it was. So here's 3 bits of information gathered from dozens of sources, textbooks, official sites: Alpha particles are identical to Helium nuclei. Alpha particle mass = 4.001506 u helium-4 nuclei mass = 4.0026032 u OK, so ... why...
  17. M

    Elastic collision with particles, find the kinetic energy

    Homework Statement A proton strikes a stationary alpha particle (4He nucleus) head-on. Assuming the collision is completely elastic, what fraction of the proton’s kinetic energy is transferred to the alpha particle? Homework Equations Pi = Pf Ki = Kf The Attempt at a Solution Tried finding...
  18. T

    Kinetic energy of an alpha particle

    Homework Statement During the ##\alpha## decay of ##^{238}_{92}U## an ##\alpha## particle is fromed inside the nucleus. Given that the last 4 nucleons in ##^{238}_{92}U## have an average binding energy per nucleon of ##6.1MeV##, estimate the kinetic energy of the ##\alpha## particle when it is...
  19. R

    Alpha particle approaching a gold nucleus

    Homework Statement An alpha particle approaches at high speeds a gold nucleus with a charge of 79e. What is the electric force acting on the alpha particle when it is 2.0e-17 m from the gold nucleus? Homework Equations FE=k(q1q2)/d2 The Attempt at a Solution FE=k(q1q2)/d2...
  20. M

    Why do 2 d not decay into alpha particle and neutral pion?

    Homework Statement The reaction dd → απ0 (where α is the Helium-4 nucleus and d denotes the deuteron) has never been observed. Why? Homework EquationsThe Attempt at a Solution [/B] So I checked first the masses to make sure energy/momentum are conserved and found out that mass of 2d is...
  21. A

    B Fusion and Alpha Particle Emission: Neutron vs Proton

    When two deuterons fuse, I understand they form an alpha particle in an excited state. Based on mass differences the fusion releases 23.85MeV, which is enough to eject a proton (19.81MeV) or a neutron (20.58MeV) from the alpha particle. It seems to prefer neutron emission, as this fusion is used...
  22. A

    Bombardment of Nitrogen-14 with an alpha particle

    Question: When alpha particles, having kinetic energy 3.0000 MeV bombard nitrogen-14 nuclei, oxygen-17 forms and the reaction releases a proton. Calculate the kinetic energy shared by the reaction products. Nitrogen-14 = 14.000307 amu Helium-4 = 4.00260 amu Oxygen-17 = 16.99913 amu Proton =...
  23. S

    What is the energy of the alpha particle and recoiling nucleus?

    Homework Statement The Q-value of alpha decay of Pu-239 is 5.244 MeV. Calculate the energy of the alpha particle in MeV. Calculate the energy of the recoil nucleus decay product in MeV. (answer correct to 3 decimal places) Homework Equations The Q value of a nuclear reaction is the difference...
  24. F

    Alpha Particle Approaching a Gold Nucleus

    Homework Statement An alpha-particle with velocity 3.5 x 106 strikes a block of gold, atomic number 79 and mass number 197. Find the distance of the closest possible approach between the alpha particle and a gold nucelus, assuming Coulomb's law holds over such distances. Assume mp = mn = 1.67 x...
  25. M

    Charged Particle in Magnetic field calculation

    Homework Statement Basically having a problem when trying to theoretically calculate the mass of alpha particle in a charged field. r is the unknown radius of curvature m = mass of an alpha particle (6.646 *10^-27 kg) v = velocity of an alpha particle immediatly after decay (1.381 *10^7 m/s)...
  26. niveda

    Proton is moving at an alpha particle, distance when it stops

    Homework Statement an alpha particle with a charge of 2e is fixed at the origin. a proton is aimed at the alpha particle and shot from a distance of 2.00 m at a speed of 3.46x10^6 m/s. How close will the proton come to the alpha particle before coming to a stop? Homework Equations Please help...
  27. Bloopy

    B Doubt regarding Rutherford's Alpha Scattering Experiment and Impact Parameter

    It is mentioned in my Textbook that if alpha-particle has large impact parameter, it gets scattered through small angles and vice versa. I understand that impact parameter is defined as the perpendicular distance between the path of a projectile and the center of the nucleus. I am unsure how...
  28. moenste

    KE of alpha particle using integer values of nuclear masses

    Homework Statement (a) Cobalt has only one stable isotope, 59Co. What form of radioactive decay would you expect the isotope 60Co to undergo? Give a reason for your answer. (b) The radioactive nuclei 21084Po emit alpha particles of a single energy, the product nuclei being 20682Pb. (b) (i)...
  29. S

    Determine the energy of an alpha particle

    I have been asked to determine the energy in MeV of an alpha particle and an Rn nucleus in the decay of Ra-226 using the conservation of energy and momentum. (assume Ra is at rest) Here is what i have done, I am just wondering if i did it properly. Thanks for your help :) Ek=kinetic energy...
  30. J

    B Cloud Chamber Experiment Help - Identifying Particles

    Yesterday I decided to carry out a cloud chamber experiment for a school assessment. I used "100%" isopropanol and around 2.5 kg of dry ice. After a wait of approximately 30 minutes, the particle tracks began to appear. I placed a weak source of Americium-241 sourced from a smoke detector (1...
  31. KT KIM

    Trajectory of scattered alpha particle

    This is a famous experiment conducted by Rutherford, in this exprement, the alpha particle(+2e charge) repulsed from necleus by coulomb force, and eventually divert its trajectory by theta. I want to show the trajectory of alpha particle has asympotes which means it go out along that asympote...
  32. Kara386

    Kinetic energy of alpha particle in alpha decay

    Homework Statement Consider the nuclear decay 21486Rn → 21084Po2- + α. Calculate the Q for this decay, and give the value of the kinetic energy of the alpha particle in the rest frame of the Rn nuclide. The rest mass of the Rn nuclide is 213.9954u, of Po is 209.9829u, of α is 4.00015u and of...
  33. P

    Distance of closest approach of alpha particle calc

    Homework Statement An alpha particle is accelerated from rest through a potential difference of 20kV. It travels directly towards a stationary Beryllium nucleus (4 protons, 5 neutrons). Calculate the distance of closest approach Homework EquationsThe Attempt at a Solution E=qv=(40x10^3)e...
  34. X

    Elastic collision between alpha particle and gold Nuclei

    Homework Statement When an alpha particle collides elastically with a nucleus, the nucleus recoils. Suppose a 3.94 MeV alpha particle has a head-on elastic collision with a gold nucleus that is initially at rest. What is the kinetic energy of (a) the recoiling nucleus and (b) the rebounding...
  35. 1

    Why we called the Helium particle as alpha particle?

    why we the alpha particle is taken as helium and beta as electron ? and what about gamma particle ? what is that? My 2nd question is that during alpha decay and beta decay there is decrease of 2 units in atomic number and one unit increase respectively ? what happen in gamma decay ?
  36. K

    How do I solve for the wavelength of an alpha particle?

    Homework Statement Compare 25-MeV alpha particles wavelengths with the size of a nucleon in a nucleus. Homework Equations λ = h/p E2 = p2c2 + m2c4 KE = ½mv2 p = mv The Attempt at a Solution To compare the wavelength of an α particle with a nucleon, I would need to divide the wavelength of...
  37. Oribe Yasuna

    Alpha Particle & Gold Nucleus Collision

    Homework Statement An alpha particle (a helium nucleus, containing 2 protons and 2 neutrons) starts out with kinetic energy of 10.5 MeV (10.5x106 eV), and heads in the +x direction straight toward a gold nucleus (containing 79 protons and 118 neutrons). The particles are initially far apart...
  38. Oribe Yasuna

    Radius of a lead nucleus and alpha particle

    Homework Statement A lead nucleus contains 207 nucleons (82 protons and 125 neutrons) packed tightly against each other. A single nucleon (proton or neutron) has a radius of about 1 ✕ 10^−15 m. (a) Calculate the approximate radius of the lead nucleus. (b) Calculate the approximate radius of...
  39. N

    Electron Capture by alpha particle -- Frequency of photon?

    Homework Statement Electron with KE = 50eV is captured by Alpha particle, ie. HE++. Calculate the frequency of the emitted photon. Homework Equations KE = m/2 v^2; E=hf, En = Z^2*-13.6eV/n^2 The Attempt at a Solution Energy before = Energy after 50eV = 4*-13.6eV/1 + hf f = 1200nm
  40. S

    Trouble using the Bethe Formula

    So I'm doing research with a professor and he wants me to use the Bethe formula to calculate stopping power for alpha particles of various energies, but I'm having a lot of trouble using it, and I figured I'd ask here before I bothered him. He wanted me to use the non-relativistic version listed...
  41. D

    Why does an alpha particle have 40mm range in air?

    Hey everyone... so I understand that an alpha particle, being a helium nucleus, is quite a large particle compared to, for example, a beta particle. Due to this, it will encounter a lot more collisions and impart its momentum to other particles of air at a much more rapid rate. Is there...
  42. abm77

    What is the speed at a great distance from the alpha particle

    Homework Statement An alpha particle has a charge of 2e and is fixed at the origin. A proton is located 2.00x10^-8 m from the alpha particle along the x-axis. When the proton is released, what is its speed at a great distance from the alpha particle q = 2e r = 2.00x10^-8 v = ? Homework...
  43. mesa

    Needing elemental alpha particle scattering/peak resonances

    On our campus we have an ion beam analysis lab. It is used for compositional analysis through the firing of alpha particles at MeV energies at target samples (RBS). From here it is a simple matter of back scattering kinematics to calculate atomic masses thereby giving the general composition of...
  44. R

    Kinetic energy of alpha particle

    Homework Statement The kinetic energy (in keV) of the alpha particle, when the nucleus 84210Po at rest undergoes alpha decay, is A 5319 B 5422 C 5707 D 5818 Homework Equations ## E = mc^2 ## Kinetic energy ## = mv^2/2 ## The Attempt at a Solution alpha particle is emission of helium nucleus...
  45. R

    Why can't an alpha particle be captured by the nucleus?

    I understand that there are many attempts from inside the nucleus to tunnel out therefore if it was just one alpha particle trying to get in it wouldn't happen. I'm struggling with this derivation from class to describe the number of attempts: How does a velocity and size of the nucleus...
  46. D

    Tunneling with an alpha particle

    Homework Statement In a simple model for a radioactive nucleus, an alpha particle (m = 6.64×10^−27kg) is trapped by a square barrier that has width 2.0*10^-15 meter and height 30.0 MeV. What is the tunneling probability if the energy of the alpha particle is 18.0MeV below the top of the...
  47. A

    Alpha particle in gold foil scatering experiment

    Homework Statement How close does the alpha particle gets to the nucleus in gold foil scatering experiment?Homework Equations Ek = 2.0 MeV W=F delta x F=(kq1q2)/r^2 W=(kq1q2)/r E=W=(kq1q2)/r The Attempt at a Solution E= (k(79)(2) e^2)/r 2.0MeV= (k(158)e^2)/r 2,000,000 eV = 8.99 Wm^2 c^-2 ((158)...
  48. E

    I knowing what i'm looking for -- alpha particle colliding with lead nucleus

    Homework Statement An alpha particle with kinetic energy 15.0MeVmakes a collision with lead nucleus, but it is not "aimed" at the center of the lead nucleus, and has an initial nonzero angular momentum (with respect to the stationary lead nucleus) of magnitude L=p0b, where p0 is the magnitude...
  49. F

    Work needed to move alpha particle

    Homework Statement Four electrons are located at the corners of a square 10.0 nm on a side, with an alpha particle at its midpoint. How much work is needed to move the alpha particle to the midpoint of one of the sides of the square? Homework Equations W = PEo-PEf PE (if several point...
  50. Evanish

    Can an Alpha Particle Fuse with a Hydrogen Atom?

    I was wondering if alpha particles created by radioactive decay ever have enough energy to fuse with something else (e.g. hydrogen or another alpha particle).