particle_class.rst

Class

The class provides an object-oriented interface to access and represent particle information.

Creating a object

The simplest way to create a object is to pass it a str representing a particle.

>>> from plasmapy.particles import Particle >>> electron = Particle('e-')

The class accepts a variety of different str formats to represent particles. Atomic symbols are case-sensitive, but element names and many aliases are not.

>>> alpha = Particle('alpha') >>> deuteron = Particle('D+') >>> triton = Particle('tritium 1+') >>> iron56 = Particle('Fe-56') >>> helium = Particle('helium') >>> muon = Particle('mu-') >>> antimuon = Particle('antimuon') >>> hydride = Particle('H-')

An int may be used as the first positional argument to to represent an atomic number. For isotopes and ions, the mass number may be represented with the mass_numb keyword and the integer charge may be represented with the Z keyword.

>>> proton = Particle(1, mass_numb=1, Z=1)

The most frequently used objects may be imported directly from the atomic subpackage.

>>> from plasmapy.particles import proton, electron

The objects that may be imported directly are: ~plasmapy.particles.proton, ~plasmapy.particles.electron, ~plasmapy.particles.neutron, ~plasmapy.particles.positron, ~plasmapy.particles.deuteron, ~plasmapy.particles.triton, and ~plasmapy.particles.alpha.

Accessing particle properties

The properties of each particle may be accessed using the attributes of the corresponding object.

>>> proton.atomic_number 1 >>> electron.charge_number -1 >>> triton.mass_number 3

Some of these properties are returned as a in SI units.

>>> alpha.charge <Quantity 3.20435324e-19 C> >>> deuteron.mass <Quantity 3.34358372e-27 kg> >>> triton.half_life <Quantity 3.888e+08 s> >>> iron56.binding_energy.to('GeV') <Quantity 0.49225958 GeV>

Strings representing particles may be accessed using the ~plasmapy.particles.particle_class.Particle.symbol, ~plasmapy.particles.particle_class.Particle.element, ~plasmapy.particles.particle_class.Particle.isotope, and ~plasmapy.particles.particle_class.Particle.ionic_symbol attributes.

>>> antimuon.symbol 'mu+' >>> triton.element 'H' >>> alpha.isotope 'He-4' >>> deuteron.ionic_symbol 'D 1+'

Categories

The ~plasmapy.particles.particle_class.Particle.categories attribute returns a set with the classification categories corresponding to the particle.

>>> sorted(electron.categories) ['charged', 'electron', 'fermion', 'lepton', 'matter', 'stable']

Membership of a particle within a category may be checked using the ~plasmapy.particles.particle_class.Particle.is_category method.

>>> alpha.is_category('lepton') False >>> electron.is_category('fermion', 'lepton', 'charged') True >>> iron56.is_category(['element', 'isotope']) True

The particle must be in all of the categories in the require keyword, at least one of the categories in the any_of keyword, and none of the categories in the exclude in order for it to return True.

>>> deuteron.is_category(require={'element', 'isotope', 'ion'}) True >>> iron56.is_category(any_of=['charged', 'uncharged']) False >>> alpha.is_category(exclude='lepton') True

Calling the ~plasmapy.particles.particle_class.Particle.is_category method with no arguments returns a set containing all of the valid categories for any particle. Valid categories include: 'actinide', 'alkali metal', 'alkaline earth metal', 'antibaryon', 'antilepton', 'antimatter', 'antineutrino', 'baryon', 'boson', 'charged', 'electron', 'element', 'fermion', 'halogen', 'ion', 'isotope', 'lanthanide', 'lepton', 'matter', 'metal', 'metalloid', 'neutrino', 'neutron', 'noble gas', 'nonmetal', 'positron', 'post-transition metal', 'proton', 'stable', 'transition metal', 'uncharged', and 'unstable'.

Conditionals and equality properties

Equality between particles may be tested either between two objects, or between a object and a str.

>>> Particle('H-1') == Particle('protium 1+') False >>> alpha == 'He-4 2+' True

The ~plasmapy.particles.particle_class.Particle.is_electron and ~plasmapy.particles.particle_class.Particle.is_ion attributes provide a quick way to check whether or not a particle is an electron or ion, respectively.

>>> electron.is_electron True >>> hydride.is_electron False >>> deuteron.is_ion True

The ~plasmapy.particles.particle_class.Particle.element and ~plasmapy.particles.particle_class.Particle.isotope attributes return None when the particle does not correspond to an element or isotope. Because non-empty strings evaluate to True and None evaluates to False when converted to a bool, these attributes may be used in conditional statements to test whether or not a particle is in one of these categories.

particles = [Particle('e-'), Particle('Fe-56'), Particle('alpha')]

for particle in particles:
    if particle.element:
        print(f"{particle} corresponds to element {particle.element}")
    if particle.isotope:
        print(f"{particle} corresponds to isotope {particle.isotope}")

Returning antiparticles

The antiparticle of an elementary particle or antiparticle may be found by either using Python's unary invert operator (~) or the ~plasmapy.particles.particle_class.Particle.antiparticle attribute of a object.

>>> ~electron Particle("e+") >>> antimuon.antiparticle Particle("mu-")