**1999 PACS, 20. - 29.
**

**
Summary of Scheme
**

20. NUCLEAR PHYSICS

**21. Nuclear Structure** (for nucleon structure,
see 14.20.D Properties of protons and neutrons;
13.40 for electromagnetic processes and properties;
13.60.H for deep-inelastic structure functions)

21.10.-k Properties of nuclei; nuclear energy levels (for properties of
specific nuclei listed by mass ranges, see 27)

21.10.Dr Binding energies and masses

21.10.Ft Charge distribution

21.10.Gv Mass and neutron distributions

21.10.Hw Spin, parity, and isobaric spin

21.10.Jx Spectroscopic factors

21.10.Ky Electromagnetic moments

21.10.Ma Level density

21.10.Pc Single-particle levels and strength functions

21.10.Re Collective levels

21.10.Sf Coulomb energies

21.10.Tg Lifetimes

21.30.-x Nuclear forces
(see also 13.75.C Nucleon-nucleon interactions)

21.30.Cb Nuclear forces in vacuum

21.30.Fe Forces in hadronic systems and effective interactions

21.45.+v Few-body systems

21.60.-n Nuclear-structure models and methods

21.60.Cs Shell model

21.60.Ev Collective models

21.60.Fw Models based on group theory

21.60.Gx Cluster models

21.60.Jz Hartree-Fock and random-phase approximations

21.60.Ka Monte Carlo models

21.65.+f Nuclear matter

***** Exotic atoms and molecules, see 36.10

21.80.+a Hypernuclei

21.90.+f Other topics in nuclear structure (restricted to new topics in
section 21)

**23. Radioactive Decay and In-beam Spectroscopy** (see also 82.55
Radiochemistry)

23.20.-g Electromagnetic transitions

23.20.En Angular distribution and correlation measurements

23.20.Gq Multipole mixing ratios

23.20.Js Multipole matrix elements

23.20.Lv Gamma transitions and level energies

23.20.Nx Internal conversion and extranuclear effects

23.20.Ra Internal pair production

23.40.-s beta decay; double beta decay; electron and muon capture

23.40.Bw Weak-interaction and lepton (including neutrino) aspects

23.40.Hc Relation with nuclear matrix elements and nuclear structure

23.50.+z Decay by proton emission

23.60.+e Alpha decay

23.70.+j Heavy-particle decay

23.90.+w Other topics in radioactive decay and in-beam spectroscopy
(restricted to new topics in section 23)

**24. Nuclear Reactions: General**

24.10.-i Nuclear-reaction models and methods

24.10.Cn Many-body theory

24.10.Eq Coupled-channel and distorted-wave models

24.10.Ht Optical and diffraction models

24.10.Jv Relativistic models

24.10.Lx Monte Carlo simulations (including hadron and parton cascades and
string breaking models)

24.10.Nz Hydrodynamic models

24.10.Pa Thermal and statistical models

24.30.-v Resonance reactions

24.30.Cz Giant resonances

24.30.Gd Other resonances

24.50.+g Direct reactions

24.60.-k Statistical theory and fluctuations

24.60.Dr Statistical compound-nucleus reactions

24.60.Gv Statistical multistep direct reactions

24.60.Ky Fluctuation phenomena

24.60.Lz Chaos in nuclear systems

24.70.+s Polarization phenomena in reactions

24.75.+i General properties of fission

24.80.+y Nuclear tests of fundamental interactions and symmetries

24.85.+p Quarks, gluons, and QCD in nuclei and nuclear processes

24.90.+d Other topics in nuclear reactions: general (restricted to new
topics in section 24)

**25. Nuclear Reactions: Specific Reactions**

25.10.+s Nuclear reactions involving few-nucleon systems

25.20.-x Photonuclear reactions

25.20.Dc Photon absorption and scattering

25.20.Lj Photoproduction reactions

25.30.-c Lepton-induced reactions

25.30.Bf Elastic electron scattering

25.30.Dh Inelastic electron scattering to specific states

25.30.Fj Inelastic electron scattering to continuum

25.30.Hm Positron scattering

25.30.Mr Muon scattering (including the EMC effect)

25.30.Pt Neutrino scattering

25.30.Rw Electroproduction reactions

25.40.-h Nucleon-induced reactions (see also 28.20 Neutron physics)

25.40.Cm Elastic proton scattering

25.40.Dn Elastic neutron scattering

25.40.Ep Inelastic proton scattering

25.40.Fq Inelastic neutron scattering

25.40.Hs Transfer reactions

25.40.Kv Charge-exchange reactions

25.40.Lw Radiative capture

25.40.Ny Resonance reactions

25.40.Qa (p,pi) reactions

25.40.Sc Spallation reactions

25.40.Ve Other reactions above meson production thresholds (energies > 400 MeV)

25.43.+t Antiproton-induced reactions

25.45.-z Sup 2 H-induced reactions

25.45.De Elastic and inelastic scattering

25.45.Hi Transfer reactions

25.45.Kk Charge-exchange reactions

25.55.-e Sup 3 H-, sup 3 He-, and sup 4 He-induced reactions

25.55.Ci Elastic and inelastic scattering

25.55.Hp Transfer reactions

25.55.Kr Charge-exchange reactions

25.60.-t Reactions induced by unstable nuclei

25.60.Bx Elastic scattering

25.60.Dz Interaction and reaction cross sections

25.60.Gc Breakup and momentum distributions

25.60.Je Transfer reactions

25.60.Lg Charge-exchange reactions

25.60.Pj Fusion reactions

25.70.-z Low and intermediate energy heavy-ion reactions

25.70.Bc Elastic and quasielastic scattering

25.70.De Coulomb excitation

25.70.Ef Resonances

25.70.Gh Compound nucleus

25.70.Hi Transfer reactions

25.70.Jj Fusion and fusion-fission reactions

25.70.Kk Charge-exchange reactions

25.70.Lm Strongly damped collisions

25.70.Mn Projectile and target fragmentation

25.70.Pq Multifragment emission and correlations

25.75.-q Relativistic heavy-ion collisions
(collisions induced by light ions studied to calibrate
relativistic heavy ion collisions, should be classified under
both 25.75 and the 13 or 25 category appropriate to the light
ions)

25.75.Dw Particle and resonance production

25.75.Gz Particle correlations

25.75.Ld Collective flow

25.80.-e Meson- and hyperon-induced reactions

25.80.Dj Pion elastic scattering

25.80.Ek Pion inelastic scattering

25.80.Gn Pion charge-exchange reactions

25.80.Hp Pion-induced reactions

25.80.Ls Pion inclusive scattering and absorption

25.80.Nv Kaon-induced reactions

25.80.Pw Hyperon-induced reactions

25.85.-w Fission reactions

25.85.Ca Spontaneous fission

25.85.Ec Neutron-induced fission

25.85.Ge Charged-particle-induced fission

25.85.Jg Photofission

25.90.+k Other topics in nuclear reactions: specific reactions (restricted
to new topics in section 25)

**26. Nuclear Astrophysics**
(see also 95.30 Fundamental aspects of astrophysics)

26.20.+f Hydrostatic stellar nucleosynthesis
(see also 97.10.C Stellar structure, interiors, evolution,
nucleosynthesis, ages)

26.30.+k Nucleosynthesis in novae, supernovae and other explosive
environments

26.35.+c Big Bang nucleosynthesis (see also 98.80.F Origin, formation, and
abundances of the elements)

26.40.+r Cosmic ray nucleosynthesis

26.50.+x Nuclear physics aspects of novae, supernovae, and other explosive
environments

26.60.+c Nuclear matter aspects of neutron stars

26.65.+t Solar neutrinos

**27. Properties of Specific Nuclei Listed by Mass Ranges** (an additional heading must be chosen with these entries, where the given mass number limits are, to some degree, arbitrary)

27.10.+h A <_ 5

27.20.+n 6 <_ A <_ 19

27.30.+t 20 <_ A <_ 38

27.40.+z 39 <_ A <_ 58

27.50.+e 59 <_ A <_ 89

27.60.+j 90 <_ A <_ 149

27.70.+q 150 <_ A <_ 189

27.80.+w 190 <_ A <_ 219

27.90.+b 220 <_ A

**28. Nuclear Engineering and Nuclear Power Studies**

28.20.-v Neutron physics (see also 25.40 Nucleon-induced reactions)

28.20.Cz Neutron scattering

28.20.Fc Neutron absorption

28.20.Gd Neutron transport: diffusion and moderation

28.41.-i Fission reactors

28.41.Ak Theory, design, and computerized simulation

28.41.Bm Fuel elements, preparation, reloading, and reprocessing

28.41.Fr Reactor coolants, reactor cooling, and heat recovery

28.41.Kw Radioactive wastes, waste disposal

28.41.My Reactor control systems

28.41.Pa Moderators

28.41.Qb Structural and shielding materials

28.41.Rc Instrumentation

28.41.Te Protection systems, safety, radiation monitoring, accidents, and
dismantling

28.50.-k Fission reactor types

28.50.Dr Research reactors

28.50.Ft Fast and breeder reactors

28.50.Hw Power and production reactors

28.50.Ky Propulsion reactors

28.50.Ma Auxiliary generators

28.52.-s Fusion reactors (for fusion reactor types, see 52.55)

28.52.Av Theory, design, and computerized simulation

28.52.Cx Fueling, heating, and ignition

28.52.Fa Materials

28.52.Lf Components and instrumentation

28.52.Nh Safety

28.60.+s Isotope separation and enrichment

28.70.+y Nuclear explosions (see also 47.40 Compressional flows; shock and
detonation phenomena; for radiation protection from fallout, see
87.52 in biological and medical physics)

28.90.+i Other topics in nuclear engineering and nuclear power studies
(restricted to new topics in section 28)

**29. Experimental Methods and Instrumentation for Elementary-particle and
Nuclear Physics**

29.17.+w Electrostatic, collective, and linear accelerators

29.20.-c Cyclic accelerators and storage rings

29.20.Dh Storage rings

29.20.Fj Betatrons

29.20.Hm Cyclotrons

29.20.Lq Synchrotrons

29.25.-t Particle sources and targets

29.25.Bx Electron sources

29.25.Dz Neutron sources

29.25.Lg Ion sources: polarized

29.25.Ni Ion sources: positive and negative

29.25.Pj Polarized and other targets

29.25.Rm Sources of radioactive nuclei

29.27.-a Beams in particle accelerators (for low energy charged-particle beams,
see 41.75)

29.27.Ac Beam injection and extraction

29.27.Bd Beam dynamics; collective effects and instabilities

29.27.Eg Beam handling; beam transport

29.27.Fh Beam characteristics

29.27.Hj Polarized beams

29.30.-h Spectrometers and spectroscopic techniques

29.30.Aj Charged-particle spectrometers: electric and magnetic

29.30.Dn Electron spectroscopy

29.30.Ep Charged-particle spectroscopy

29.30.Hs Neutron spectroscopy

29.30.Kv X- and gamma-ray spectroscopy

29.30.Lw Nuclear orientation devices

***** Energy loss and stopping power, see 34.50.B
and 61.85

29.40.-n Radiation detectors (for mass spectrometers, see 07.75)

29.40.Cs Gas-filled counters: ionization chambers, proportional, and avalanche
counters

29.40.Gx Tracking and position-sensitive detectors

29.40.Ka Cherenkov detectors

29.40.Mc Scintillation detectors

29.40.Rg Nuclear emulsions

29.40.Vj Calorimeters

29.40.Wk Solid-state detectors

29.50.+v Computer interfaces (for electronic circuits, see 84.30)

29.85.+c Computer data analysis

29.90.+r Other topics in elementary-particle and nuclear physics
experimental methods and instrumentation (restricted to new topics
in section 29)