Recoil factor measurement

The paper summerizes the experimental data on the equilibrium factor, F, the free fraction, fp, the attachment rate to the room air aerosol, X, the recoil factor,, and the plateout rates of the free, qf, and the attached, q3, radon daughters, determined in eight rooms of different houses. In each room several measurements were carried out at different times, with different aerosol sources (cigarette smoke, stove heating etc.) and under low (v<0.3 It1) and moderate (0.3[Pg.288]

The recoil factors r define the probability of whether an attached radioactive atom desorbs from the particle surface in consequence of an alpha decay or not. Mercer and Strowe (1971) found a recoil factor = 0.81 in their chamber studies in contradiction to the value of ri 0.4 measured by Kolerski et al. (1973). No other results about the recoil factor are available in the literature. 

Finally with the measured values of c a, cja and cj- the recoil factor rx can be calculated ... 

Table lb. The equilibrium factor (F), the free fraction (fp), the attachment parameters (X,0,d), the plateout rates (qf, qa) and the recoil factor (r ), calculated from the measured data of Table la (lo i/ ventilation). 

The subject of the recoil-free fraction was initially discussed in Mossbauer s original paper (Mossbauer, 1958). Since then, many books and review articles (e.g. Nussbaum, 1966) have been devoted to describing experimental measurements and theoretical calculations of the recoil-free fraction f Hence this discussion will be limited to some of the major aspects of the information obtainable from /-factor measurements. The measurement itself is relatively easy, since for thin absorbers the Mossbauer spectral area is proportional to /, and thus the relative change in / with temperature is readily obtainable. With thick absorbers one can still obtain accurate values, although the analysis requires transmission integrals (Shenoy, 1973). 

However, in contrast, the resonance effect increased by cooling both the source and the absorber. Mdssbauer not only observed this striking experimental effect that was not consistent with the prediction, but also presented an explanation that is based on zero-phonon processes associated with emission and absorption of y-rays in solids. Such events occur with a certain probability/, the recoil-free fraction of the nuclear transition (Sect. 2.4). Thus, the factor/is a measure of the recoilless nuclear absorption of y-radiation - the Mdssbauer effect. 

The recoil-free fraction /a of transition metal complexes or proteins in frozen solution can be as small as 0.1-0.3, when measured just below the melting point, but the /-factor increases strongly when the temperature is lowered to fiquid nitrogen temperatures (77 K), and at fiquid helium temperatures (4.2 K) it may reach values of 0.7-0.9 [35]. This makes a substantial difference to the acquisition time of the spectra because of the square dependency on the signal (3.1). 

Wender and Hershkowitz [237] used the sensitivity of the recoil-free fraction in tungsten Mossbauer spectroscopy to deduce the effect of irradiation of tungsten compounds by Coulomb excitation of the resonance levels (2 states of I82,i84,i8 y with 6 MeV a-particles. While no effect of irradiation on the/-factors could be observed for tungsten metal in agreement with [233], a decrease of/was measured for WC, W2B, W2B5, and WO3 after irradiation. 

Due to the suppression factor the difference of the leading Dirac and recoil contribution of the RHS in (12.10) may be calculated with high accuracy, and practically does not depend on the exact value of the Rydberg constant. Then the precise magnitude of the linear combination of the Lamb shifts on the RHS extracted from the experimentally measured frequencies on the LHS and calculated difference of the leading Dirac and recoil contribution of... 

We have performed an experiment to measure the g factor of the electron bound to a Carbon nucleus in a Hydrogen-like C5+ ion [9]. As shown below, the result of our measurement represents a significant test of bound state QED contributions and also accounts for the recoil correction from the finite mass of the carbon nucleus. The experiments are performed on single C5+ ions confined in a Penning ion trap at low temperatures, almost completely isolated from the environment. As outlined in the last paragraph the extension of our experiments to other highly charged systems opens a number of possibilities for future measurements of fundamental quantities such as the electrons mass or the fine structure constant. 

The curve shows the factor E which is a measure of the recoil-less fraction of the implanted atoms at 30 K. At very low temperatures this fraction is small, indicating a nearly complete disorder around the position of the Kr. 

The energy lost by the neutron was absorbed in making the molecule recoil and is called the recoil energy, Ej. In the case of the methane molecule, measured at a momentum transfer of 9 A , the recoil energy would be (the eonversion factor from A to cm 16.7, was introduced in Eq. (2.21)). 

The above illustrations and discussion lead us to several general conclusions concerning the use of neutron spectroscopy in the study of torsional vibrations (and other large-amplitude modes) in molecular systems. First, the neutron technique-since it involves the interaction of neutrons with vibrating nuclei and is especially sensitive to large amplitude motions—can for appropriate molecules be an ideal complement for optical spectroscopy. Neutron spectroscopy, however, is hampered somewhat by the available instrumental resolution ( 10 cm-1) and by the inherent recoil resolution broadening in fluid-phase spectra. In addition, present accessibility of instrumentation for the neutron method (for low k molecular spectroscopy) is limited. For example, there are only a few reactors in the United States where appropriate instruments and intensity exist for such measurements (neutron sources and instrumentation amenable to the study of crystal and liquid structure and interatomic and intermolecular dynamics are more accessible). These factors make it imperative that studies of molecular systems be chosen with some care. 

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