D. Humbert, Yu. Ralchenko, P. Krstic and R. E. H. Clark, "Classification of Processes, Version 1.2, 7 October 2003", IAEA Atomic and Molecular Data Unit, unpublished.
As explained in the introduction there it was produced in order to synthesize classifications used in on-line databases CFADC, AMBDAS and GAPHYOR. For convenience I reproduce the classification here in plain text format. Note that it is not presented as exactly a Thesaurus. One would probably want to remove the three-letter codes, and then one has to disambiguate some terms (e.g. Recombination) that occur under two or more headings. Treat the non-bold terms as NT1 refinements of the bold terms for the purpose of a Thesaurus. I have a few further comments at the bottom.
Structure and Spectra
SGN - General
SLS - Line broadening, shapes and shifts
SIA - Interatomic Potentials
SPM - Polarizabilities, Electric Moments
SEW - Energy Levels and Wavelengths
STP - Transition Probabilities and Oscillator Strengths
SSM - Potential Curves and Structure of Molecules
SDP - Dynamic Polarizability
SIR - Infrared Spectra
SVS - Visible Spectra
SUV - UV/VUV/XUV Spectra
SXR - X-Ray Spectra
SRS - Rotational Spectra
SVB - Vibrational Spectra
SAI - Autoionization
SAD - Autodetachment
SDS - Autodissociation
SMM - Magnetic Moments
SHF - Hyperfine Structure
SIE - Isoelectronic Sequences
SFT - Forbidden Transitions
SQE - QED Effects
SRP - Relaxation Processes
SIP - Ionization Potentials
SRY - Rydberg States
Photon-Particle and Field-Particle Interactions
PGN - General
PTS - Total Absorption, Scattering
PDS - Photodissociation
PES - Elastic Scattering
PMA - Multiphoton Absorption (excitation and ionization)
PDT - Photodetachment
PFL - Fluorescence
PEX - Photoexcitation
PIN - Photoionization
PFF - Free-Free Absorption or Inverse Bremsstrahlung
PEA - Effective Absorption, Total Diffusion
PTA - True Absorption
PAD - Angular Diffusion (scattering)
PED - Elastic Diffusion (Thomson, Rayleigh)
PNL - Non-linear Effects
PZE - Zeeman Effect
PSE - Stark Effect
PGF - General Electromagnetic Field
PTF - Interaction with Time-Varying Fields
Electron-Heavy Particle Interactions
EGN - General
EAS - Angular Scattering
EBS - Bremsstrahlung
EDX - Deexcitation
EEL - Elastic Scattering
ELB - Line Broadening, Shapes and Shifts
ETS - Total Scattering
EDT - Detachment
EFL - Fluorescence
EEX - Excitation, Change of Excitation
EIN - Ionization
EMI - Multiple Ionization
ENI - Negative Ion Formation
EMT - Momentum Transfer, Transport Cross-Sections
EUP - Unknown Products
EDP - Depolarization, Change of Polarization
EIP - Creation of an ion pair (positive-negative)
ERC - Recombination (general)
ERR - Radiative Recombination
ERD - Dielectronic Recombination
ERT - 3-body Recombination
ERO - e-i-o Recombination
EDC - Dielectronic Capture
EDS - Dissociation
EDR - Dissociative Recombination
EDA - Dissociative Attachment
EDE - Dissociative Excitation
EDI - Dissociative Ionization
Heavy Particle-Heavy Particle Interactions
HGN - General
HAS - Association
HLB - Line Broadening, Shapes and Shifts
HDS - Dissociation
HDX - Deexcitation
HES - Elastic Scattering
HCX - Charge Transfer
HUP - Unknown Products
HAS - Angular Scattering (sic, also Association)
HIR - Interchange Reactions
HEL - Inelastic Energy Losses
HET - Energy Transfer
HIP - Interaction Potentials
HRC - Recombination
HTS - Total Scattering
HDT - Detachment
HFL - Fluorescence
HEX - Excitation
HIN - Ionization
HPN - Penning Ionization
HST - Stripping (of projectile)
HAT - Attenuation
HXT - Excitation Transfer
HAI - Associative Interchange Reactions
HDI - Dissociative Interchange Reactions
HDC - Dissociative Charge Transfer
HMN - Mutual Ion-Ion Neutralization
Particle-Matter Interactions
MGN - General
MAC - Accomodation
MAD - Adsorption
MCR - Chemical Reactions
MDE - Desorption
MRE - Reemission
MRF - Reflection
MSD - Surface Damage
MSE - Secondary Electron Emission
MIR - Radiation Induced by Particle Impact on Surfaces
MNE - Neutralization, Ionization, Dissociation
MSP - Sputtering
MRS - Radiation-Enhanced Sublimation
MTD - Trapping, Detrapping
MPE - Photoelectric Ejection of Electrons
MEL - Energy Loss and Stopping Power
MPR - Particle Range
MMS - Multiple Scattering
MCP - Charge State Population
MEP - Excited State Population
MRH - Reflection of Heavy Particles from Surfaces
MRL - Reflection of Electrons from Surfaces
Data Compilations
DGN - General
DEH - Electron-Heavy Particle Interactions
DHH - Heavy Particle-Heavy Particle Interactions
DPF - Photon-Particle and Field-Particle Interactions
DSS - Structure and Spectra
DTP - Transport Properties
DPM - Particle-Matter Interactions
Bibliography
BGN - General
BEH - Electron-Heavy Particle Interactions
BHH - Heavy Particle-Heavy Particle Interactions
BPF - Photon-Particle and Field-Particle Interactions
BSS - Structure and Spectra
BTP - Transport Properties
BPM - Particle-Matter Interactions
Further comments by BJB.
At the top level of this classification the items Photon-Particle and Field-Particle Interactions, Electron-Heavy Particle Interactions, Heavy Particle-Heavy Particle Interactions, and Particle-Matter Interactions characterize the incoming channel of the reaction and the next level in the classification describes the process or outcoming channel. The description of the incoming channel could of course be refined (heavy-heavy reactions can be refined into atom-atom, atom-molecule, molecule-molecule, and then further by charge of the involved particles). The reason that this was not done will lie in the intended application of this classification to a specific collection of databases. In those databases one searches by reactants and by process; so, for example, one searches for collisions of (e-) with (N2)+, and process dissociative ionization. There is no need for a specific category of, say, Electron-(Positive Molecular Ion) Collisions if the user is anyway specifying the reactants.
Without reproducing it here I also point to the process codes developed by the Virtual Atomic and Molecular Data Centre (VAMDC) for use with the XML Schema for Atoms, Molecules and Solids (XSAMS):