The classification codes are threeletter abbreviations, the first letter indicating the general group of processes to which a process belongs (e.g. E for electronheavy particle interactions). In the examples, A, B and C refer to an arbitrary atom and n an arbitrary integer greater than 1.
EAE  Auger Electron Ejection  Electronimpact induced Auger electron ejection 
e^{} + A → A**^{+} + 2e^{}; A**^{+} → A*^{2+} + e^{} 
EAS  Angular Scattering  Differential electronscattering cross sections, usually as a function of energy and angle. 

EBS  Bremsstrahlung  The emission of electromagnetic radiation by a charged particle as it is decelerated through Coulomb interactions with other charges; "freefree" radiation in the context of plasma physics. 
e^{} + A → e^{} + A + hν 
EDA  Dissociative Attachment  Dissociative attachment 
e^{} + AB → A + B^{} 
EDC  Dielectronic Capture  Dielectronic capture 
e^{} + A^{+} → A** 
EDE  Dissociative Excitation  Electronimpact dissociative excitation 
e^{} + AB → A* + B + e^{} 
EDI  Dissociative Ionization  Electronimpact dissociative ionization 
e^{} + AB → A^{+} + B + 2e^{} 
EDP  Depolarization, Change of Polarization  Electronimpact change of polarization, including depolarization 

EDR  Dissociative Recombination  Electronimpact dissociative recombination 
e^{} + AB^{+} → A + B 
EDS  Dissociation  Electronimpact dissociation 
e^{} + AB → A + B + e^{} 
EDT  Electron Detachment  Electronimpact detachment 
e^{} + A^{} → A + 2e^{} 
EDX  Deexcitation  Generic inelastic collisional processes in which a scattered electron gains energy from the target particle. 
e^{} + A^{*} → e^{} + A 
EEL  Elastic Scattering  Scattering of an electron with no change in energy. 
e^{} + A → e^{} + A 
EEX  Excitation  Electronimpact excitation 
e^{} + A → e^{} + A^{*} 
EEX  Change of Excitation  Electronimpact change of excitation. Deprecated: Use EEX: Excitation or EDX: Deexcitation instead. 
e^{} + A^{*} → e^{} + A^{**} 
EFL  Fluorescence (Optical Emission)  Total optical emission following electronimpact events 

EGN  General  General electronimpact processes that do not fall into any more specific category. 

EHT  Transport  Transport cross sections: momentum, viscosity and higherorder. 

EIN  Ionization  Electron impact ionization 
e^{} + A → A^{+} + 2e^{} 
EIP  IonPair Formation  Electronimpact induced formation of a (positive, negative) ion pair 
e^{} + AB^{+} → A^{+} + B^{} 
ELB  Line Broadening, Shapes and Shifts  Data relating to the line shapes and positions of radiative transitions 

EMI  Multiple Ionization  Electronimpact ionization to a charge state greater than +1 
e^{} + A → A^{n+} + (n+1)e^{} 
EMT  Momentum Transfer  Electron impact momentum transfer 

ENI  Negative Ion Formation  Electronimpact formation of negative ion (attachment) 
e^{} + A → A^{} 
ERC  Recombination  Electronimpact recombination 
e^{} + A^{n+} → A^{(n1)+} 
ERD  Dielectronic Recombination  Electronimpact dielectronic recombination 
e^{} + A^{+} → A** → A* + hν 
ERO  ElectronIonOther Recombination  Electronion recombination involving a third body other than an electron 
e^{} + A^{+} + B → A + B 
ERR  Radiative Recombination  Electronimpact recombination with radiative emission 
e^{} + A^{+} → A + hν 
ERT  ThreeBody Recombination  Electronimpact threebody recombination 
e^{} + e^{} + A^{+} → A + e^{} 
ERV  Rovibrational Excitation  Electronimpact rovibrational excitation 
e^{} + AB → e^{} + AB (v=*; J=*) 
ESF  SpinFlip  Electronimpact change of spin state 
e^{} + ^{[S]}A → e^{} + ^{[S']}A 
ETS  Total Scattering  Total electron scattering cross sections 

EUP  Unknown Products  Electronimpact collision with unknown products. Deprecated: use EGN (General) instead. 

EXE  Electronic Excitation  Electronimpact electronic excitation 
e^{} + AB → e^{} + AB* 
EXR  Rotational Excitation  Electronimpact rotational excitation 
e^{} + AB → e^{} + AB (J=*) 
EXV  Vibrational Excitation  Electronimpact vibrational excitation 
e^{} + AB → e^{} + AB (v=*) 
PAD  Scattering  Photon scattering ( angular diffusion) 

PAE  Auger Electron Ejection  Photoninduced Auger electron ejection 
A + hν → A**^{+} + e^{}; A**^{+} → A*^{2+} + e^{} 
PCS  Compton Scattering  Inelastic scattering of a photon by a charged particle that decreases the photon energy. 

PDP  Depolarization, Change of Polarization  Photoninduced change of polarization, including depolarization 

PDS  Photodissociation  Photodissociation of a molecule 
hν + AB → A + B 
PDT  Photodetachment  Absorption of a photon inducing the removal of an electron from an anion to form a neutral species. 
hν + A^{} → A + e^{} 
PEA  Effective Absorption, Total Diffusion  Effective Absorption, Total Diffusion of photons 

PED  Elastic Diffusion  Photon elastic diffusion processes (Thomson scattering, Rayleigh scattering) 

PES  Elastic Scattering  Scattering of a photon with no change in energy. 
hν + A → hν + A 
PEX  Photoexcitation  Photon absorption leading to excitation 
hν + A → A* 
PFF  Inverse Bremsstrahlung  Acceleration of a charged particle by a photon absorption process mediated by an electronparticle Coulomb interaction; "freefree absorption" in the context of plasma physics. 
e^{} + A + hν → A + e^{} 
PFL  Fluorescence  Fluorescence 
A* → A + hν 
PGF  General Electromagnetic Field  Miscellaneous effects induced by an electromagnetic field 

PGN  General  General photonparticle interaction processes which do not fall into any more specific category 

PIN  Photoionization  Photoninduced ionization 
hν + A → A^{+} + e^{} 
PIP  IonPair Formation  Photoninduced formation of a (positive, negative) ion pair 
AB + hν → A^{+} + B^{} 
PMA  Multiphoton Excitation  Absorption of more than one photon, leaving to excited and/or charged products 
nhν + A → A^{+}/A*/A*^{+} 
PNL  NonLinear Effects  Nonlinear radiative effects 

PRD  Radiative Decay  Radiative decay (not necessarily fluorescence) 
A* → A + hν 
PRV  Rovibrational Excitation  Photoninduced rovibrational excitation 
BC + hν → BC (v=*; J=*) 
PSE  Stark Effect  Spectral linesplitting caused by an external electric field 

PTA  True Absorption  True Absorption of a photon 

PTF  Interaction with TimeVarying Fields  General interactions with timevarying fields 

PTS  Total Absorption, Total Scattering  Total photon absorption or scattering cross sections. 

PXE  Electronic Excitation  Photoninduced electronic excitation 
BC + hν → BC* 
PXR  Rotational Excitation  Photoninduced rotational excitation 
BC + hν → BC (J=*) 
PXV  Vibrational Excitation  Photoninduced vibrational excitation 
BC + hν → BC (v=*) 
PZE  Zeeman Effect  Spectral linesplitting caused by a static magnetic field 
HAC  Association  Heavyparticle collision leading to association (i.e. bond formation) 
A + B → AB 
HAI  Associative Ionization  Heavy particle impact associative ionization 
A + B → AB^{+} + e^{} 
HAR  Radiative Association  Heavy particle impact radiative ionization 
A + B → AB + hν 
HAS  Angular Scattering  Heavyparticle differential scattering cross sections, usually as a function of energy and angle. 

HAT  Attenuation  Attenuation 

HCX  Charge Transfer  Heavyparticle impact leading to chargetransfer. 
A^{+} + B → A + B^{+}; A^{} + B → A + B^{} 
HDC  Dissociative Charge Transfer  Heavyparticle dissociative charge transfer 
A^{+} + BC → A + B^{+} + C 
HDE  Dissociative Excitation  Heavy particle impact dissociative excitation 
A + BC → A* + B + C; A + BC → A + B + C* 
HDI  Dissociative Ionization  Heavy particle impact dissociative ionization 
A + BC → A^{+} + B + C; A + BC → A + B^{+} + C 
HDN  Dissociative Neutralization  Heavy particle impact dissociative neutralisation 
AB^{} + C+ → A + B + C 
HDS  Dissociation  Heavyparticle impact leading to dissociation (bondbreaking) 
A + BC → A + B + C 
HDT  Detachment  Heavyparticle collisions leading to electronic detachment. 
A + B^{} → A + B + e^{} 
HDX  Deexcitation  Heavyparticle impact leading to deexcitation (decrease of total internal energy). 
A* + B → A + B 
HEL  Inelastic Energy Losses  Heavyparticle collisions leading to inelastic energy loss. 

HES  Elastic Scattering  Scattering of heavy particles with no change in energy. 
A + B → A + B 
HET  Energy Transfer  Heavyparticle collisions with energy transfer between the particles. 

HEX  Excitation  Heavyparticle impact leading to excitation (increase of total internal energy). 
A + B → A* + B 
HFL  Fluorescence  Heavy particle collisional excitation followed by radiative decay. 
A + B → A* + B; A* → A + hν 
HGN  General  General heavyparticle collisional processes which do not fall into any more specific category 

HHT  Transport  Heavy particle transport cross sections: momentum, viscosity and higherorder. 

HIN  Ionization  Heavyparticle collisions leading to ionization 
A + B → A + B^{+} + e^{} 
HIP  Interaction Potentials  Interaction potentials between heavy particles. 

HIR  Interchange Reactions  Heavyparticle interchange reactions 
A + BC → AB + C 
HLB  Line Broadening, Shapes and Shifts  Data relating to line shapes and positions determined by heavyparticle collisions. 

HMI  Multiple Ionization  Heavy particle impact ionization with a charge state change greater than +1 
A + B → A^{n+} + (n+1)e^{} + B 
HMN  Mutual IonIon Neutralization  Neutralization of heavyparticle ions. 
A^{+} + B^{} → A + B 
HMT  Momentum Transfer  Heavy particle momentum transfer 

HPN  Penning Ionization  Ionization through collision of an internallyexcited heavyparticle with another heavy particle. 
A* + B → A + B^{+} + e^{} 
HRC  Recombination  Heavyparticle collisions with recombination 

HRV  Rovibrational Excitation  Heavy particle impact rovibrational excitation 
A + BC → A + BC (v=*; J=*) 
HST  ElectronStripping  Ionization of the projectile in a heavyparticle collision. 
A + B → A^{+} + B + e^{} 
HTE  Electron Transfer  Heavyparticle electron transfer 
A^{} + B → A + B^{} 
HTI  Transfer Ionization  Transfer of an electron from an atom to an ion, followed by further ionization. 
A + B^{+} → A^{2+} + B + e^{} 
HTS  Total Scattering  Total heavy particle scattering cross sections 

HUP  Unknown Products  Heavyparticle collisions/reactions with unknown products. 
A + B → ? 
HXE  Electronic Excitation  Heavy particle impact electronic excitation 
A + BC → A + BC* 
HXF  FineLevel Excitation  Heavy particle impact finelevel excitation 
A + B → A + B (J=*) 
HXH  Hyperfine Excitation  Heavy particle impact hyperfinelevel excitation 
e^{} + AB → e^{} + AB (F=*) 
HXR  Rotational Excitation  Heavy particle impact rotational excitation 
A + BC → A + BC (J=*) 
HXT  Excitation Transfer  Transfer of internal excitation in a heavyparticle collision. 
A* + B → A + B* 
HXV  Vibrational Excitation  Heavy particle impact vibrational excitation 
A + BC → A + BC (v=*) 
SAD  Autodetachment  Autodetachment in atoms and molecules 

SAI  Autoionization  Autoionization processes in atoms and molecules. 

SDP  Dynamic Polarizability  Dynamic polarizability of atoms and molecules 

SDS  Autodissociation  Autodissociation in atoms and molecules 

SEW  Energy Levels and Wavelengths  Energy levels and transition frequencies / wavelengths of atoms and molecules. 

SFT  Forbidden Transitions  Forbidden transitions in atoms and molecules 

SGN  General  General spectral processes and structural properties that do not fall into any more specific category 

SHF  Hyperfine Structure  Hyperfine structure of atoms and molecules 

SIA  Interatomic Potentials  Interatomic Potentials as they relate to the spectral or structural properties of atoms or molecules. 

SIE  Isoelectronic sequences  Isoelectronic sequences of atoms 

SIP  Ionization Potentials  Ionization potentials of atoms and molecules. 

SIR  Infrared Spectra  Infrared spectra of atoms and molecules 

SLS  Line Broadening, Shapes and Shifts  Data relating to line shapes and positions with a focus on spectroscopy or atomic/molecular structure. 

SMM  Magnetic Moments  Magnetic moments (dipolar, quadrupolar, etc.) of atoms and molecules. 

SPM  Polarizabilities, Electric Moments  Polarizabilities and electric moments (dipolar, quadrupolar, etc.) of atoms and molecules. 

SQE  QED Effects  QED effects in atoms and molecules 

SRA  Raman spectroscopy  Raman spectroscopy of atoms and molecules. 

SRP  Relaxation Processes  Relaxation processes in atoms and molecules. 

SRS  Rotational Spectra  Rotational spectra of molecules 

SRY  Rydberg States  Rydberg states of atoms and molecules. 

SSM  Potential Curves and Structure of Molecules  Potential energy curves/surfaces and molecular structure data. 

STP  Transition Probabilities and Oscillator Strengths  Transition probabilities (Einstein Afactors), oscillator strengths and line intensities of radiative transitions in atoms and molecules. 

SUV  UV/VUV/XUV Spectra  UV spectra of atoms and molecules from ~10 nm (extreme ultraviolet) to ~400 nm (near ultraviolet). 

SVB  Vibrational Spectra  Vibrational spectra of molecules 

SVS  Visible Spectra  Visible spectra of atoms and molecules 

SXR  XRay Spectra  XRay spectra of atoms and molecules 
MAC  Accomodation  Accomodation 

MAD  Adsorption  Adsorption on a surface 

MBS  Backscattering  Backscattering from a surface 

MCP  Charge State Population  Charge state population of condensed materials. 

MCR  Chemical Reactions  Chemical reactions at a surface 

MCS  Chemical Sputtering  Chemical sputtering of surfaces. 

MDE  Desorption  Desorption from a surface. 

MDP  Deposition  Deposition on a surface. 

MEL  Energy Loss and Stopping Power  Energy loss and stopping power of materials with respect to a flux of particles. 

MEP  Excited State Population  Excited state population of condensed materials. 

MER  Erosion  Erosion of a surface (over a longer timescale than sputtering) 

MGN  General  General particlematter interaction processes that do not fall into any more specific category. 

MIR  ParticleImpact Induced Radiation  Radiation induced by particle impact on surfaces. 

MMS  Multiple Scattering  Multiple scattering of particles within a material. 

MNE  Neutralization, Ionization, Dissociation  Neutralization, ionization or dissociation at a surface. 

MPE  Photoelectric Ejection of Electrons  Ejection of electrons due to incoming radiation (the photoelectric effect). 

MPM  Permeation  Permeation of particles through a solid 

MPR  Particle Range  Data relating to the particle transmission through a material. 

MPS  Physical Sputtering  Physical sputtering of surfaces. 

MRE  Reemission  Reemission of accommodated particles at a surface 

MRF  Reflection  Reflection of particles from a surface. 

MRH  Reflection of Heavy Particles from Surfaces  Reflection of heavy particles from surfaces 

MRL  Reflection of Electrons from Surfaces  Reflection of electrons from surfaces 

MRS  RadiationEnhanced Sublimation  Radiationenhanced sublimation of solids. 

MSD  Surface Damage  Surface damage of a surface due to impinging particles over a short timescale. 

MSE  Secondary Electron Emission  Secondary electron emission from a surface. 

MSI  Surface Interactions  Interactions at surfaces. 

MSP  Sputtering  Sputtering of surface material by impinging particles 

MTD  Trapping, Detrapping  Trapping and detrapping of accommodated particles in a solid. 

MTR  Transmutation  Transmutation of nuclei in solid material by impact of subatomic particles. 

MVP  Vapour Formation and Properties  Formation and properties of vapour in front of a surface; in the context of plasma physics, vapour shielding phenomena. 
DEH  ElectronHeavy Particle Interactions  Data compilations concerning electronheavy particle interactions. 

DGN  General  General data compilations that do not fall into any more specific category. 

DHH  Heavy ParticleHeavy Particle Interactions  Data compilations concerning heavy particleheavy particle interactions. 

DPF  PhotonParticle and FieldParticle Interactions  Data compilations concerning photonparticle and fieldparticle interactions. 

DPM  ParticleMatter Interactions  Data compilations concerning particlematter interactions. 

DSS  Structure and Spectra  Data compilations concerning atomic and molecular structure and spectra. 

DTP  Transport Properties  Data compilations concerning transport properties. 
BEH  ElectronHeavy Particle Interactions  Bibliographic data resources concerning electronheavy particle interactions. 

BGN  General  General bibliographic data resources that do not fall into any more specific category. 

BHH  Heavy ParticleHeavy Particle Interactions  Bibliographic data resources concerning heavy particleheavy particle interactions. 

BPF  PhotonParticle and FieldParticle Interactions  Bibliographic data resources concerning photonparticle and fieldparticle interactions. 

BSS  Structure and Spectra  Bibliographic data resources concerning atomic and molecular structure and spectra. 

BTP  Transport Properties  Bibliographic data resources concerning transport properties. 
COM  Composite Process with Multiple Channels  Process occuring through multiple channels with no uniquelydefined products. For example, the summed cross section of ionization and chargeexchange. 
A + B → A^{n+} 