Nuclear Physics

The existence of the nucleus: Rutherford Experiment

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Isotopes and Nuclides

Models of the nucleus Liquid drop model

Alpha particle model

Non-central force Spectroscopic model Problem: which potential ??

Decay Law: Half life Blue Stable elements; Green Radioactive elements with very long-lived isotopes. Their half-live of over four million years confers them very small, if not negligible radioactivities; Yellow Radioactive elements that may present low health hazards. Their most stable isotopes have half-lives between 800 and years. Because of this, they usually have some commercial applications; Orange Radioactive elements that are known to pose high safety risks. Their most stable isotopes have half-lifes between one day and 103 years. Their radioactivities confers them little potential for commercial uses; Red Highly radioactive elements. Their most stable isotopes have half-lifes between one day and several minutes. They pose severe health risks. Few of them receive uses outside basic research; Purple Extremely radioactive elements. Very little is known about these elements due to their extreme instability and radioactivity.

Penetration Depth The energy of radiation is typically measured in MeV, mega electronvolt:. If a beam of photons with intensity I 0 traverses a layer of material of thickness x, the intensity emerging from the layer is where  is called the linear absorption coefficient. It is related to the cross section  for photon absorption by where N A is Avogadro’s constant and  is the density of the material.

Radioactivity UnitsGray [Gy] absorbed dose: energy deposited per unit mass of medium[J/kg] Sievert [Sv]risk from ionizing radiation radradiation absorbed dose remroentgen eq. mammal (to gauge bio effects) The number of radioactive nuclei of an isotope varies in radioactive decay according to where N is the number of nuclei at t=0, N 0 the remaining number at t, and is the decay constant. T 1/2 is the half-life, the time from t=0 when half the original nuclei remain.  decay

Safety After low to moderate radiation poisoning [1-6 Gy] within hoursnausea and vomiting diarrhea possibly headache and fever With increasing dose cognitive impairment Mortality 5-100%; above 6 Gy > 50% Primary dangers: (whole body exposure) immunodeficiency destruction of bone marrow shortage of white blood cells

Weighting factors W R for equivalent dose: how dangerous are types of radiation? Radiation Energy w R x-ray,  -ray, e -, e +,  n< 10 keV5 < 100 keV10 < 2 MeV20 higher< 20 P> 2 MeV2 , fission fragments, heavy nuclei20