Irradiation with a-Particles

Frederick Joliot and Irene Curie discussed the "/-rays emitted in association with neutrons by berillium irradiated with a particles and reported to have observed under the same conditions also the emission of fast positrons. The origin of these particles was not yet clear at the time of the Solvay Conference. It was understood by the same authors a few months later when they discovered the artificial radioactivity induced by a-particle bombardment which normally takes place by emission of positrons. 

Remarkably selective excitation of the A 3n (f = 6) level has been observed in a number of reaction systems. Some years ago, Herzberg [157] suggested that an inverse predissociation might be responsible, but this proposal is incompatible with the modern value of D0 (C2) and has been replaced by the proposal [153] that crossing from the 3S state takes place. The band progression from A 3Na(v = 6), often called the high-pressure bands, is observed when <0.01 % of CO in He is irradiated with a particles [158], The reaction... 

The nmax barrier can be overcome in several ways by gradually increasing capillary pressure until pa >nmax is reached (see Section 3.3.3) by adding electrolyte in the initial solution until Ceicr is reached by applying external disturbance which facilitates overcoming nmax and can be realised by local heating or irradiating with a-particles. 

For formation of heavier elements irradiation with a particles is preferable, because by (o , n) or (a, 2n) reactions the atomic number increases by two units ... 

The elements with the atomic numbers 97 and 98 (berkelium and californium) at first could not be produced by irradiation with neutrons, because isotopes of Cm exhibiting jfi" transmutation were not known. After milligram amounts of " Am had been produced by reaction (14.14), was obtained in 1949 by Thompson, Ghiorso and others by irradiation with a particles ... 

For the production of elements with atomic numbers Z > 101 irradiation with ions of atomic numbers Z > 2 is necessary, because for irradiation with a particles actinides with adequate half-lives which can be used as targets are not available. Two concepts for the synthesis of new, heavy nuclides can be distinguished ... 

Thus Avrami [71] reviewed radiation effects on explosives, propellants and pyrotechnics. Here are some of the main conclusions taken from the work of Avrami and numerous authors initiating explosives are decomposed under irradiation with a-particles, neutrons, 7-radiation, electron irradiation and underground testing. Among the reviewed papers Avrami reported his own work on the influence of Co gamma radiation on the detonation velocity of explosives they all show a fall in velocity after irradiation. Cyclonite (EDX) appears to be particularly sensitive, less sensitive are PETN and HMX. Aromatic compounds such as TNT and Tetryl seem to be still less sensitive. 

Fig. 4. Smoothing of tho surface of copper by irradiation with a particles (121). Electron micrographs of surface replicas, magnification ca. 50,000. Left-hand column typical areas before irradiation. Right-hand column tjrpical areas after 5 x 10 a/cm. (Areas shown are not the same before and after but are typical of each condition.)...

When the polydisperse silver nanoparticles are irradiated with a monochromatic light, only the nanoparticles that are resonant with the incident light are excited and the excited electrons are transferred to Ti02, giving rise to liberation of Ag. The resonant particles are thus reduced in size until they become non-resonant. Some of the electrons... 

Silver nanoparticles can be deposited on Ti02 by UV-irradiation. Deposition of polydisperse silver particles is a key to multicolor photochromism. The nanoparticles with different size have different resonant wavelength. Upon irradiation with a monochromatic visible light, only the resonant particle is excited and photoelectrochemically dissolved, giving rise to a decrease in the extinction at around the excitation wavelength. This spectral change is the essence of the multicolor photochromism. The present photoelectrochemical deposition/dissolution processes can be applied to reversible control of the particle size. 

Purrott, R.J., A.A. Edwards, D.C. Lloyd, and J.W. Stather, The Induction of Chromosome Aberrations in Human Lymphocytes by in Vitro Irradiation With Alpha-Particles From Pu 239, Internat. J. Radiation Biology 38 277-284 (1980). 

All the separation methods mentioned in this article, and, in general, the. chemical treatment, can be equally well applied to targets which have been irradiated with other particles, for example in a linear accelerator or cyclotron. 

Using the Columbia microbeam, Zhou et al. [4] passed one alpha particle through the nuclei of mammalian cells. When 10% of the cells were irradiated with a single alpha particle, the mutation yield was similar to that observed when 100% of the cells were irradiated. Clearly, a single alpha particle can induce genomic instability in cells that were not irradiated. 

As shown by the investigations of a number of authors, irradiation of lead azide (and other azides) with a-particles, X-rays and y-rays does not cause explosion (Ha issinsky and Walden [89] Gunther, Lepin and Andreyev [90]). However, it produces a slow decomposition of lead azide, according to Kaufman [91]. 

Irradiation with charged particles accelerated in a cyclotron, while eliminating the problem of long-lived silver isotopes caused by the different nuclear reactions involved, is not feasible for any large-scale study because of the cost involved. Unlike a nuclear reactor, where numerous different samples can be irradiated simultaneously, only a single sample can be irradiated using a cyclotron beam. 

Bowden and Singh (Refs 28 35) irradiated Pb azide, Cd azide, Ag azide, Li azide and Ag acetylide with a particles but failed to cause... 

Wu JC, Stubbe J, Kozarich JW (1985b) Mechanism of bleomycin evidence for 4 -ketone formation in poly(dA-dU) associated exclusively with base release. Biochemistry 24 7569-7573 Wu LJ, Randers-Pehrson G, Xu A, Waldren CA, Yu Z, Yu Z, Hei TK (1999) Targeted cytoplasmic irradiation with alpha particles induces mutations in mammalian cells. Proc Nat Acad Sci USA... 

Track-etch membranes were developed by the General Electric Corporation Schenectady Laboratory [3], The two-step preparation process is illustrated in Figure 3.4. First, a thin polymer film is irradiated with fission particles from a nuclear reactor or other radiation source. The massive particles pass through the film, breaking polymer chains and leaving behind a sensitized track of damaged polymer molecules. These tracks are much more susceptible to chemical attack than the base polymer material. So when the film is passed through a solution... 

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