Nuclear Physics
Nuclear Physics Henri Becquerel (185-1908) accidentally discovered radioactivity in uranium compounds in 1896. Uranium salt crystals darkened a light-tight photographic plate.
Nuclear Physics Henri Becquerel (185-1908) accidentally discovered radioactivity in uranium compounds in 1896. Uranium salt crystals darkened a light-tight photographic plate. Milestones in development of nuclear physics
Nuclear Physics Henri Becquerel (185-1908) accidentally discovered radioactivity in uranium compounds in 1896. Uranium salt crystals darkened a light-tight photographic plate. Milestones in development of nuclear physics Rutherford et al. in 1919 observed first nuclear reaction: α-particle + N O
Nuclear Physics Henri Becquerel (185-1908) accidentally discovered radioactivity in uranium compounds in 1896. Uranium salt crystals darkened a light-tight photographic plate. Milestones in development of nuclear physics Rutherford et al. in 1919 observed first nuclear reaction: α-particle + N O discovery of the neutron by Chadwick in 193
Nuclear Physics Henri Becquerel (185-1908) accidentally discovered radioactivity in uranium compounds in 1896. Uranium salt crystals darkened a light-tight photographic plate. Milestones in development of nuclear physics Rutherford et al. in 1919 observed first nuclear reaction: α-particle + N O discovery of the neutron by Chadwick in 193 discovery of artificial radioactivity by Joliot & Irene Curie in 1933
Nuclear Physics Henri Becquerel (185-1908) accidentally discovered radioactivity in uranium compounds in 1896. Uranium salt crystals darkened a light-tight photographic plate. Milestones in development of nuclear physics Rutherford et al. in 1919 observed first nuclear reaction: α-particle + N O discovery of the neutron by Chadwick in 193 discovery of artificial radioactivity by Joliot & Irene Curie in 1933 discovery of nuclear fission by Hahn & Strassman in 1938
Nuclear Physics Henri Becquerel (185-1908) accidentally discovered radioactivity in uranium compounds in 1896. Uranium salt crystals darkened a light-tight photographic plate. Milestones in development of nuclear physics Rutherford et al. in 1919 observed first nuclear reaction: α-particle + N O discovery of the neutron by Chadwick in 193 discovery of artificial radioactivity by Joliot & Irene Curie in 1933 discovery of nuclear fission by Hahn & Strassman in 1938 development of first controlled-fission reactor by Fermi et al. in 194
Components of nuclei: protons and neutrons
Components of nuclei: protons and neutrons How we represent a nucleus: A Z X
Components of nuclei: protons and neutrons How we represent a nucleus: A Z X Z atomic number ( number of protons)
Components of nuclei: protons and neutrons How we represent a nucleus: A Z X Z atomic number ( number of protons) A mass number total number of nucleons (protons + neutrons)
Components of nuclei: protons and neutrons How we represent a nucleus: A Z X Z atomic number ( number of protons) A mass number total number of nucleons (protons + neutrons) A Z number of neutrons
Components of nuclei: protons and neutrons How we represent a nucleus: A Z X Z atomic number ( number of protons) A mass number total number of nucleons (protons + neutrons) A Z number of neutrons Isotopes: same Z but different A
Components of nuclei: protons and neutrons How we represent a nucleus: A Z X Z atomic number ( number of protons) A mass number total number of nucleons (protons + neutrons) A Z number of neutrons Isotopes: same Z but different A C, C, C, C... 11 6 1 6 13 6 14 6
Components of nuclei: protons and neutrons How we represent a nucleus: A Z X Z atomic number ( number of protons) A mass number total number of nucleons (protons + neutrons) A Z number of neutrons Isotopes: same Z but different A C, C, C, C... 11 6 1 6 13 6 14 6 Unified mass unit: 1 6 C atom is exactly 1 u: 1 u 1.66 10-7 kg
Components of nuclei: protons and neutrons How we represent a nucleus: A Z X Z atomic number ( number of protons) A mass number total number of nucleons (protons + neutrons) A Z number of neutrons Isotopes: same Z but different A C, C, C, C... 11 6 1 6 13 6 14 6 Unified mass unit: 1 6 C atom is exactly 1 u: 1 u 1.66 10-7 kg Note: 1 u 931.5 MeV/c
Size of nuclei
Size of nuclei r
Size of nuclei r Tightly-packed spherical nucleons
Size of nuclei r liquid-drop model Nuclei have almost same density, independent of A Tightly-packed spherical nucleons
Size of nuclei r Tightly-packed spherical nucleons liquid-drop model Nuclei have almost same density, independent of A 1/ 3 r r 0 A
Size of nuclei r Tightly-packed spherical nucleons liquid-drop model Nuclei have almost same density, independent of A 1/ 3 r r 0 A r 0 1. 10-15 m 1. fm
Size of nuclei r Tightly-packed spherical nucleons liquid-drop model Nuclei have almost same density, independent of A 1/ 3 r r 0 A r 0 1. 10-15 m 1. fm Rutherford s experiment
Size of nuclei r Tightly-packed spherical nucleons liquid-drop model Nuclei have almost same density, independent of A 1/ 3 r r 0 A r 0 1. 10-15 m 1. fm Rutherford s experiment a-particle Au
Size of nuclei r Tightly-packed spherical nucleons liquid-drop model Nuclei have almost same density, independent of A 1/ 3 r r 0 A r 0 1. 10-15 m 1. fm Rutherford s experiment CAPA Set #13: #3 a-particle Au
Size of nuclei r liquid-drop model Nuclei have almost same density, independent of A 1/ 3 r r 0 A Tightly-packed spherical nucleons r 0 1. 10-15 m 1. fm Rutherford s experiment CAPA Set #13: #3 a-particle 3. 10-14 m Au
Nuclear stability
Nuclear stability With strong Coulomb repulsion of protons, how can a nucleus exist?
Nuclear stability With strong Coulomb repulsion of protons, how can a nucleus exist? Nuclear force: short range ~ fm and strongly attracts all nucleons
Nuclear stability With strong Coulomb repulsion of protons, how can a nucleus exist? Nuclear force: short range ~ fm and strongly attracts all nucleons
Nuclear stability With strong Coulomb repulsion of protons, how can a nucleus exist? Stable nuclei Nuclear force: short range ~ fm and strongly attracts all nucleons
Nuclear stability With strong Coulomb repulsion of protons, how can a nucleus exist? Stable nuclei Nuclear force: short range ~ fm and strongly attracts all nucleons As A increases, need N > Z so that nuclear force due to extra neutrons offsets increasing Coulomb-repulsion
Nuclear stability With strong Coulomb repulsion of protons, how can a nucleus exist? Stable nuclei Nuclear force: short range ~ fm and strongly attracts all nucleons As A increases, need N > Z so that nuclear force due to extra neutrons offsets increasing Coulomb-repulsion Known unstable nuclei (radioactive)
Radioactivity
Radioactivity a-particle: 4 He nucleus
Radioactivity a-particle: 4 He nucleus b-ray: electron (e - ) or positron (e + )
Radioactivity a-particle: 4 He nucleus b-ray: electron (e - ) or positron (e + ) g-ray: high-energy photon
Radioactivity a-particle: 4 He nucleus b-ray: electron (e - ) or positron (e + ) g-ray: high-energy photon increasing penetration
Radioactivity a-particle: 4 He nucleus b-ray: electron (e - ) or positron (e + ) g-ray: high-energy photon increasing penetration 39 94 Pu is hazardous for chemical and radiation-damage reasons, in addition to being used in fission weapons.
Radioactivity a-particle: 4 He nucleus b-ray: electron (e - ) or positron (e + ) g-ray: high-energy photon increasing penetration 39 94 Pu is hazardous for chemical and radiation-damage reasons, in addition to being used in fission weapons. Pu emits α-particles (not dangerous outside body)
Radioactivity a-particle: 4 He nucleus b-ray: electron (e - ) or positron (e + ) g-ray: high-energy photon increasing penetration 39 94 Pu is hazardous for chemical and radiation-damage reasons, in addition to being used in fission weapons. Pu emits α-particles (not dangerous outside body), but is chemically similar to calcium seeks bone marrow where α-particles can do significant somatic damage.
Radioactivity a-particle: 4 He nucleus b-ray: electron (e - ) or positron (e + ) g-ray: high-energy photon increasing penetration 39 94 Pu is hazardous for chemical and radiation-damage reasons, in addition to being used in fission weapons. Pu emits α-particles (not dangerous outside body), but is chemically similar to calcium seeks bone marrow where α-particles can do significant somatic damage. α-particles will not penetrate the dead layers of your skin. Thus Pu is hard to detect because it only emits α-particles.
Nuclear decay constant & half life
Nuclear decay constant & half life Can t predict when a given nucleus will decay, but a large population acts predictably.
Nuclear decay constant & half life Can t predict when a given nucleus will decay, but a large population acts predictably. Let N number of nuclei at this instant
Nuclear decay constant & half life Can t predict when a given nucleus will decay, but a large population acts predictably. Let N number of nuclei at this instant Over a short time interval t, let N be change in N (# of decays).
Nuclear decay constant & half life Can t predict when a given nucleus will decay, but a large population acts predictably. Let N number of nuclei at this instant Over a short time interval t, let N be change in N (# of decays). N λ N t
Nuclear decay constant & half life Can t predict when a given nucleus will decay, but a large population acts predictably. Let N number of nuclei at this instant Over a short time interval t, let N be change in N (# of decays). N λ N t decay constant: s -1, min -1, yr -1
Nuclear decay constant & half life Can t predict when a given nucleus will decay, but a large population acts predictably. Let N number of nuclei at this instant Over a short time interval t, let N be change in N (# of decays). N λ N t decay constant: s -1, min -1, yr -1 Decay rate R N t λ N
Nuclear decay constant & half life Can t predict when a given nucleus will decay, but a large population acts predictably. Let N number of nuclei at this instant Over a short time interval t, let N be change in N (# of decays). N λ N t decay constant: s -1, min -1, yr -1 Decay rate R N t λ N N N 0 e λ t
Nuclear decay constant & half life Can t predict when a given nucleus will decay, but a large population acts predictably. Let N number of nuclei at this instant Over a short time interval t, let N be change in N (# of decays). N λ N t decay constant: s -1, min -1, yr -1 Decay rate R N t λ N N N t 0 e λ e.718
Half life T1/
Half life T 1/ N 1 0 λ T / λ T1/ λ T1/ N0e 1 e e ln() λ T 1/
Half life T 1/ N 1 0 λ T / λ T1/ λ T1/ N0e 1 e e ln() λ T 1/
Half life T 1/ N 1 0 λ T / λ T1/ λ T1/ N0e 1 e e ln() λ T 1/
Half life T 1/ N 1 0 λ T / λ T1/ λ T1/ N0e 1 e e ln() λ T 1/
Half life T 1/ N 1 0 λ T / λ T1/ λ T1/ N0e 1 e e ln() λ T 1/ 0.693 λ T1/
Half life T 1/ N 1 0 λ T / λ T1/ λ T1/ N0e 1 e e ln() λ T 1/ 0.693 λ T1/ 0.693 T 1/ λ
Half life T 1/ N 1 0 λ T / λ T1/ λ T1/ N0e 1 e e ln() λ T 1/ 0.693 λ T1/ 0.693 T 1/ λ λ 0.693 T1/
Half life T 1/ N 1 0 λ T / λ T1/ λ T1/ N0e 1 e e ln() λ T 1/ 0.693 λ T1/ 0.693 T 1/ λ λ 0.693 T1/ 14 6 10 C 1 Carbon dating: for living things, 11 C 7.6 1 6
Half life T 1/ N 1 0 λ T / λ T1/ λ T1/ N0e 1 e e ln() λ T 1/ 0.693 λ T1/ 0.693 T 1/ λ λ 0.693 T1/ 14 6 10 C 1 Carbon dating: for living things, 11 C 7.6 1 6 14 6 C emits β-rays relatively easy to detect
Half life T 1/ N 1 0 λ T / λ T1/ λ T1/ N0e 1 e e ln() λ T 1/ 0.693 λ T1/ 0.693 T 1/ λ λ 0.693 T1/ 14 6 10 C 1 Carbon dating: for living things, 11 C 7.6 1 6 14 6 C emits β-rays relatively easy to detect 14 6 C : T1/ 5730 years
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample?
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt ln(0.75) ln() T 1/ t 0.88
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt ln(0.75) ln() T 1/ t 0.88
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt ln(0.75) ln() T 1/ t 0.88
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt 0.88 T ln() ln(0.75) ln() T 0.88 5730y 0.693 1/ / t 1 t 0.88 380 yr
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt 0.88 T ln() ln(0.75) ln() T 0.88 5730yr 0.693 1/ / t 1 t 0.88 380 yr
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt 0.88 T ln() ln(0.75) ln() T 0.88 5730yr 0.693 1/ / t 1 t 0.88 380 yr
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt 0.88 T ln() ln(0.75) ln() T 0.88 5730yr 0.693 1/ / t 1 t 0.88 380 yr Example : suppose you had 14 µg of 14 C ( 1 µ mole). What is the number of decays per second?
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt ln(0.75) ln() T 1/ t 0.88 Example : suppose you had 14 µg of 14 C ( 1 µ mole). What is the number of decays per second? R λ N 0.88 T ln() ln() T 1/ N 0.88 5730yr 0.693 / t 1 ln() T 1/ 380 yr ( 6 3) 6 10 6.0 10.3 10 decays/s
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt ln(0.75) ln() T 1/ t 0.88 Example : suppose you had 14 µg of 14 C ( 1 µ mole). What is the number of decays per second? R λ N 0.88 T ln() ln() T 1/ N 0.88 5730yr 0.693 / t 1 ln() T 1/ 380 yr ( 6 3) 6 10 6.0 10.3 10 decays/s
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt ln(0.75) ln() T 1/ t 0.88 Example : suppose you had 14 µg of 14 C ( 1 µ mole). What is the number of decays per second? R λ N 0.88 T ln() ln() T 1/ N 0.88 5730yr 0.693 / t 1 ln() T 1/ 380 yr ( 6 3) 6 10 6.0 10.3 10 decays/s
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt ln(0.75) ln() T 1/ t 0.88 Example : suppose you had 14 µg of 14 C ( 1 µ mole). What is the number of decays per second? R λ N 0.88 T ln() ln() T 1/ N 0.88 5730yr 0.693 / t 1 ln() T 1/ 380 yr ( 6 3) 6 10 6.0 10.3 10 decays/s
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt ln(0.75) ln() T 1/ t 0.88 Example : suppose you had 14 µg of 14 C ( 1 µ mole). What is the number of decays per second? R λ N 0.88 T ln() ln() T 1/ N 0.88 5730yr 0.693 / t 1 ln() T 1/ 380 yr ( 6 3) 6 10 6.0 10.3 10 decays/s A unit of activity R is called a curie: 1 Ci 3.7 10 10 decays/s
Example 1: old sample of vegetation with 14 C content of 0.75 of that expected from present-day samples. How old is sample? 0.75 e λt ln(0.75) ln() T 1/ t 0.88 Example : suppose you had 14 µg of 14 C ( 1 µ mole). What is the number of decays per second? R λ N 0.88 T ln() ln() T 1/ N 0.88 5730yr 0.693 / t 1 ln() T 1/ 380 yr ( 6 3) 6 10 6.0 10.3 10 decays/s A unit of activity R is called a curie: 1 Ci 3.7 10 10 decays/s Activity.3 10 3.7 10 6 10 6 µ Ci