Stopping power and continuous-slowing-down range
Stopping power S(E)=−dE/dℓ is the mean energy loss per path length in a specified material.
Key knowledge
Stopping power S(E)=−dE/dℓ is the mean energy loss per path length in a specified material. Collision/electronic loss involves excitation and ionization, nuclear stopping involves target recoil, and radiative loss includes bremsstrahlung where relevant. Neglecting energy-loss fluctuations, the continuous-slowing-down path range is R_CSDA(E₀)=∫₀^E₀dE/S(E); it differs from the projected depth along the initial direction when scattering deflects the particle.
Values and equations
S(E)=−dE/dℓ; R_CSDA(E₀)=∫₀^E₀dE/S(E); S_mass=S/ρ; R_mass=ρR_CSDA
- E,E₀
- Particle kinetic energy and initial value J
- ℓ,R_CSDA
- Path length and mean-loss path-range model m
- S
- Positive mean stopping power J m⁻¹
- ρ
- Homogeneous material density kg m⁻³
- S_mass
- Mass stopping power J m² kg⁻¹
- R_mass
- Mass path range kg m⁻²
Conditions and scope
- S(E)>0 and a finite integral over the stated energy interval; specified particle, material/density and stopping model. The use of a mean loss does not reproduce energy straggling, individual tracks or an exact endpoint.
- Mass stopping power S/ρ has units J m² kg⁻¹ and mass range ρR has units kg m⁻² for homogeneous density ρ. The NIST electron/proton/helium database's component approximations and tabulated energy ranges are not universal statements about every particle at all energies.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
National Institute of Standards and Technology (NIST)2 sources
Evidence and review
ESTAR/PSTAR/ASTAR: stopping-power and range definitions: Appendix: full definitions of collision, radiative, nuclear and total stopping power, CSDA reciprocal-stopping integral, projected range and detour factor; no numerical database output is claimed. ESTAR/PSTAR/ASTAR: program outputs: Section 3.2: mass stopping-power and range output dimensions, converted here from MeV cm²/g and g/cm² to SI units.
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