Muoniated Radicals Research Articles

Muon Spin Rotation Studies of Enediynes

Muon spin rotation spectra of muoniated radicals of the enediyne compounds (E)- and (Z)-RC⋮CCHCHC⋮CR where R = −CH2CH2CH2CH3 are reported and the temperature variation of these spectra from 250 to 400 K investigated. All primary radicals expected were observed and assigned using ab initio DFT calculations. The properties of a six membered secondary radical likely to be formed by the cyclization of the muoniated Z-isomer were estimated using an ab initio DFT calculation.

A strategy for the measurement of the vibrations of a muoniated radical centre: experimental evidence.

A strategy for the measurement of the vibrations of a muoniated radical centre: experimental evidence.

A muoniated radical in selenium

We report new 0.3 T transverse-field μSR experiments in crystalline Se which show only a small, slowly relaxing muon signal at 300 K , accounting for about 30% of the incoming muon polarization. However, at 90 K signals are observed around 74 and 157 MHz , characteristic of a radical with a hyperfine coupling of 231 MHz . Very fast relaxation which increases with temperature makes these signals impossible to follow beyond 200 K . Above 400 K a quickly relaxing diamagnetic signal becomes visible, its relaxation falling with increasing temperature. In the melt (>490 K) just a single non-relaxing diamagnetic signal is seen. These observations may be explained by electron spin-exchange with a muoniated radical.

Muoniated radicals in the organic semiconductor zinc-phthalocyanine

μSR experiments were conducted on the organic semiconductor zinc-phthalocyanine (Zn-Pc) in order to identify and characterize the muon states in this material. Transverse-field experiments at 0.5 mT reveal the existence of paramagnetic muon states in Zn-Pc, with the formation probability of nearly 100%. Two different muoniated radicals were detected, with hyperfine parameters of 127 and 142 MHz; muonium is thus bound to the Zn-Pc molecule at two different sites. Preliminary longitudinal field measurements indicate the onset of spin dynamics above 200 K. The observed relaxation is interpreted as due to spin exchange scattering with charge carriers.