Title: impact parameter
Long Title: IUPAC Gold Book - impact parameter
DOI: 10.1351/goldbook.I02987
Status: current
Index: quantity

Definition
In simple hard sphere collision theory the distance of closest approach that would result for two particles in a collision if the particle trajectories were undeflected by the collision.

Related Term
- collision theory: https://goldbook.iupac.org//terms/view/C01170

Sources
- Green Book, 2nd ed., p. 56 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
- PAC, 1991, 63, 1541. 'Recommendations for nomenclature and symbolism for mass spectroscopy (including an appendix of terms used in vacuum technology). (Recommendations 1991)' on page 1555 (https://doi.org/10.1351/pac199163101541)
- PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 168 (https://doi.org/10.1351/pac199668010149)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/I02987/html
- json: https://goldbook.iupac.org/terms/view/I02987/json
- xml: https://goldbook.iupac.org/terms/view/I02987/xml

Citation: Citation: 'impact parameter' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.I02987
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Accessed: 2026-08-07T12:02:26+00:00