Muon spin relaxation methods

Ohira S, Shimizu Y, Kanoda K, Saito G (2006) Spin liquid state in k-(BEDT-TTF)2Cu2(CN)3 studied by muon spin relaxation method. J Low Temp Phys 142 153-158... 

Snider is best known for his paper reporting what is now referred to as the Waldmann-Snider equation.34 (L. Waldmann independently derived the same result via an alternative method.) The novelty of this equation is that it takes into account the consequences of the superposition of quantum wavefunctions. For example, while the usual Boltzmann equation describes the collisionally induced decay of the rotational state probability distribution of a spin system to equilibrium, the modifications allow the effects of magnetic field precession to be simultaneously taken into account. Snider has used this equation to explain a variety of effects including the Senftleben-Beenakker effect (i.e., is, the magnetic and electric field dependence of gas transport coefficients), gas phase NMR relaxation, and gas phase muon spin relaxation.35... 

More recently, longitudinal muon spin relaxation was used to measure rate constants for the reactions of organic radicals with molecular oxygen and with NO in the gas phase [32, 46]. The reactions are important in combustion processes and for the degradation of organic pollutants in the atmosphere. Accurate determinations by conventional techniques have often proved to be non-trivial, so that the muon technique appears to be a very valuable addition to the tool box of experimental methods. 

Recently, Larkin et al. (2000) have encountered (in a study of the spin-ladder system Sr(Cui xZnj )203, which falls outside this review, but see sect. 8.3.4) muon spin relaxation functions with too shallow and too broad minima of polarization to be reproduced by Kubo-Toyabe functions. Again, longitudinal field data showed the spin system to be static. These authors used an approach (called Kubo golden rule, KGR), which was originally derived by Kubo (see Kubo 1981 and Yamazaki 1997) to describe their findings. For details we refer to the original papers. The KGR method allows the calculation of the muon spin relaxation function for arbitrary field distributions (if they can be described by arithmetic function). In the spin-ladder compound an exponential field distribution reproduced the data. The approach of Noakes and Kalvius (1997) can be reproduced using KGR. 

Another new microscopic technique which can determine in principle S(q,t) in spin glasses is the measurement of muon spin relaxation (juSR). Here the q dependenees are not tunable as in the NSE method (eq. 70) but are broadly averaged over all q. The window of relaxation times seen by ptSR spans the 10 " s to 10 s regime, and henee partly overlaps with that of the neutron techniques (10 s to 10 s). 

IMC inverse Monte Carlo (method) gSR muon spin relaxation... 

The relaxation effects as probed via the Mossbauer hyperfine interaction can be investigated by other methods which can be regarded as complementary to Mossbauer spectroscopy. The techniques of perturbed angular correlation of gamma rays (PAC) and positive muon spin rotation (pSR) spectroscopy will be briefly discussed here. A more detailed review can be found in Dattagupta (1981). 

Retaining the theme of metal carbonyl clusters, capping considerations in transition-metal clusters have been discussed with reference to [Sb2Co4(CX))] g( A-CX))], and [Bi2Co4(CO)jQ( i-CO)]" 28. An infrared spectroscopic study of the formation of carbonyl rhodium clusters on a rhodium electrode produced by oxidation reduction cycles in acidic solution 2 has also been published. Electrochemistry with ruthenium carbonyls >21 osmium carbonyls 2 jg also reported. Muon spin rotation in a metal-cluster carbonyl compound has been communicated and, lastly, a proton spin-lattice NMR relaxation study of hydride carbonyl clusters has been reported. This provides a method for determining distances involving hydrido ligands... 

Muon spin resonance spectroscopy is an offshoot of the experiment that proved parity nonconservation in pion and muon decay. The observation that the initial amplitudes and the relaxation rates of the muon precession signals depended on the nature of the stopping medium led to a new analytical method that is closely related to Fourier transform magnetic resonance. 

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