In order to supply radiobiologists with realistic data, the space and time evolution of each chemical species created by or set in motion during the slowing down of electrons and photons in biological media were derived. In order to obtain this kind of process in water three Monte Carlo type codes were combined. For low energy photons (a few eV to 10KeV) methods of calculating differential and total cross sections for molecular gases were developed and used in transport codes.
IN ORDER TO SUPPLY THE RADIOBIOLOGIST WITH DATA MORE REALISTIC THAN THE SPATIAL DISTRIBUTION OF THE ENERGIES DEPOSITED AND THE NUCLIDES CREATED BY LOW-ENERGY (10 EV TO 30 KEV) ELECTRONS AND PHOTONS IN THE BIOLOGICAL MEDIUM, WE INTEND TO STUDY, BY COMPUTER SIMULATION METHODS, THE DEVELOPMENT OF PRIMARY AND SECONDARY NUCLIDES CREATED ALONG TRAJECTORIES, AS A FUNCTION OF TIME. IN OTHER WORDS, WE WANT TO INTRODUCE THE PHYSICOCHEMICAL STAGE, WHICH TAKES PLACE BETWEEN 10 TO THE POWER OF MINUS 13 AND 10 TO THE POWER OF MINUS 6 SECOND, INTO OUR MONTE CARLO PROGRAMMES. FOR THAT WE HAVE TO TAKE INTO ACCOUNT ATOMIC REORGANIZATION (WHICH WE HAVE ALREADY SIMULATED, BUT NOT AS A FUNCTION OF TIME), RECOMBINATION, ATTACHMENT AND DETACHMENT RATES, REACTIONS BETWEEN THE NUCLIDES CREATED AND INTERMOLECULAR ENERGY TRANSFERS. WE WILL BEGIN WITH THE GASES FOR WHICH THERE ARE DATA, GO ON TO EXAMINE WATER IN VAPOUR FORM AND THEN IN THE LIQUID STATE, AND FINALLY CONSIDER BIOLOGICAL EQUIVALENT MEDIA OR, IF POSSIBLE, BIOLOGICAL MEDIA THEMSELVES. AT THE SAME TIME, THE CODES FOR CALCULATING THE PRIMARY EFFECTS OF PHOTONS AND ELECTRONS WILL BE IMPROVED IN THE RANGE 0-1 KEV BY TAKING INTO ACCOUNT EXPERIMENTAL AND THEORETICAL EFFECTIVE CROSS-SECTIONS WHICH HAVE RECENTLY BECOME AVAILABLE.