Ionizing radiation curie

Lind (1961) defines radiation chemistry as the science of the chemical effects brought about by the absorption of ionizing radiation in matter. It can be said that in 1895, along with X-rays, Roentgen also discovered the chemical action of ionizing radiation. He drew attention to the similarity of the chemical effects induced by visible light and X-rays on the silver salt of the photographic plate. This was quickly followed by the discovery of radioactivity of uranium by Becquerel in 1896. In 1898, the Curies discovered two more radioactive elements—polonium and radium. 

About 1910, M. Curie suggested that ions were responsible for the chemical effects of radioactive radiations. Soon thereafter, mainly due to the pioneering work of Lind on gases, the notation M/N was introduced for a quantitative measure of the radiation effect, where N is the number of ion pairs formed and M is the number of molecules transformed—either created or destroyed. This notation, referred to as the ion pair yield, was most conveniently employed in gases where N is a measurable quantity. However, for some time the same usage was extended to condensed systems assuming that ionization did not depend on the phase. This, however, is not necessarily correct. The notation G was introduced by Burton (1947) and others to denote the number of species produced or destroyed per 100 eV absorption of ionizing radiation. In this sense, it is defined... 

Lind [2] has defined radiation chemistry as the science of the chemical effects brought about by the absorption of ionizing radiation in matter. It should be distinguished from radiation damage which refers to structural transformation induced by irradiation, particularly in the solid state. The distinction is not always maintained, perhaps unconsciously, and sometimes both effects may be present simultaneously. Following a suggestion of M. Curie around 1910, that ions were responsible for the chemical effects of radioactive radiations, the symbol MjN was introduced to quantify the radiation chemical effect, where M is the number of molecules transformed (created or destroyed) and N is the number of ion pairs formed. Later, Burton [3] and others advocated the notation G for the number of species produced or destroyed per 100 eV (= 1.602 x 10 J) absorption of ionizing radiation. It was purposely defined as a purely experimental quantity independent of implied mechanism or assumed theory. 

Amounts of radioactivity are designated in terms of rads, roentgens, curies, disintegrations per unit time (minute), or counts per unit time (minute). The relationships between these various unit designations are summarized in Table 3-3. The first two units are rarely used except for measuring human exposure to ionizing radiation. It is worthy of emphasis... 

Several terms are used to express the intensity of radiation (see Figure 9.8). Radiation level is a term often substituted for dose rate or exposure rate. It is generally referred to as the effect of radiation on matter i.e., the amount of radiation that is imparted from the source and absorbed by matter due to emitted radiation per unit of time. The curie is a radiological term for the physical amount of a radioactive material. A curie consists of 37 billion disintegrations per second. It is a physical amount of material that is required to produce a specific amount of ionizing radiation ... 

Physica.1 The energy level of ionizing radiation is measured as megaelectron volts (MeV). The amount of ionizing radiation released by a material regardless of the type of radiation has the measure curie (Ci) in British Units. In metric units the measure is becquerel (Bq). A curie (Ci) is the amount of radioactive material that has a disintegration rate of 3.7 X 10 °atoms/s. 

X rays were discovered by German physicist Wilhelm Rontgen in 1895, and radiation emitted from uranium and other radioactive elements was discovered by French physicists Henri Becquerel, Marie Curie, and Pierre Curie shortly thereafter. Patents were issued for food preservation using ionizing radiation in 1905 and for the use of X rays to destroy Trichinella in pork in 1921. 

The most prominent application of nonpolar liquids is their use as detection media in liquid ionization chambers for ionizing radiation. The concept of a liquid-filled conductivity cell for the detection of radioactive radiation or X-rays was first realized almost 100 years ago. In 1897, J.J. Thomson reported that vaseline oil showed an increase in electrical conductivity under irradiation with X-rays (Thomson, 1897). A few years later, P. Curie studied the influence of radium radiation on the electrical conductivity of several nonpolar liquids (Curie, 1902). Later, gas-filled ionization chambers and counters and solid-state devices became the dominating detectors for ionizing radiation and elementary particles. 

The term radioactivity was proposed by Marie Curie to describe the emission of ionizing radiation by some of the heavier elements. Ionizing radiation, as the name implies, interacts with matter to produce ions. This means that the radiation is sufficiently energetic to break chemical bonds. Some ionizing radiation is particulate (consisting of particles), and some is nonparticulate. We introduced a, j8, and 7 radiation in Section 2-2. Let s describe them again in more detail, together with two other nuclear processes. 

T n 1962 the U. S. Army opened at its Natick Laboratories in Natick, Mass., the world s largest irradiation laboratory (2) for preserving foods by ionizing energy (Figure 1). This laboratory is unique in that, in addition to having two radiation sources, a 24-m.e.v., 18-kw. electron linear accelerator and a 1,250,000-curie cobalt-60 isotope source, it includes a food development-preparation laboratory and an experimental development kitchen (Figure 2). 

There are three names coimected with the discovery of radioactivity Henry Bec-querel, who discovered this phenomenon in 1896 [2] Maria Sklodowska-Curie, who named this process radioactivity and her husband Pierre Curie [3]. They stated that uranium salts emit ionizing rays and, furthermore, Maria Sklodowska-Curie discovered that thorium gives off the same rays. She proved that radiation was not the outcome of some interaction of molecules, but must come from an atom itself this discovery was absolutely revolutionary. Maria and Pierre discovered the first two radioactive elements, polonium and radium. There are about 20 radioactive elements and about 50 radionuclides in the natural environment. 

Curie = A physical amount of radioactive material 1 Megacurie (MCI) = 1,000,000 Curies 1 Kilocurie (kCi) = 1,000 Curies 1 Millicurie (mCi) = 0.0001 Curies 1 Microcurie (uCi) = 0.000001 Curies Roentgen = Ionization per cm of dry air RAD = Radiation absorbed dose — Dosage REM = Biological effects... 

While a curie is a measure of the physical amount, the roentgen is a measure of the amount of ionization produced by a specific material. It is the amount of x-ray or gamma radiation that produces 2 billion ionizations in 1 cm of dry air. A RAD is the radiation-absorbed dose (roughly equal to a roentgen). The radiation equivalent man (REM), also roughly equal to a roentgen, is a term for how much radiation has been absorbed, or the biological effect of the dose. 

The Joliot-Curies decided next to see if the beryllium radiation would knock protons out of matter as alpha particles did. They fitted their ionization chamber with a thin window, explains Feather, and placed various materials close to the window in the path of the radiation. They found nothing, except with materials such as paraffin wax and cellophane which already contained hydrogen in chemical combination. When thin layers of these substances were close to the window, the current in the ionization chamber was greater than usual. By a series of experimental tests, both simple and elegant, they produced convincing evidence that this excess ionization was due to protons ejected from the hydrogenous material. The Joliot-Curies understood then that what they were seeing were elastic collisions—like the collisions of billiard balls or marbles—between the beryllium radiation and the nuclei of H atoms. 

Polonium, element 84 on the periodic table, was a strange metal. Marie and Pierre Curie had isolated it by hand from pitchblende residues (at backbreaking concentrations of a tenth of a milligram per ton of ore) in 1898 and named it in honor of Marie Curie s native Poland. Physically and chemically it resembled bismuth, the next element down the periodic table, except that it was a softer metal and emitted fi ve thousand times as much alpha radiation as an equivalent mass of radium, which caused the ionized, excited air around a pure sample to glow with an unearthly blue hght. 

---