M. Camani

The detection of muonium in water

Abstract We report the first direct observation of the muonium atom (μ + e − ) in a liquid sample. Using the transverse field μSR technique muonium spin precession signals were detected in water at six different fields between 4 and 80 G.

Bimolecular rate constants for reactions of muonium in aqueous solutions

Abstract Rate constants have been obtained from the rates of disappearance of the muonium precession signal in aqueous solutions of KMnO 4 , NaNO 3 , NaOH, NaCl, HCl, HClO 4 , maleic acid and ethanol. They disagree with the results of earlier, indirect determinations. Comparison with the rate constants for hydrogen atoms reveals large kinetic isotope effects.

New determination of the magnetic moment of the positive muon from Larmor precession measurements in liquid bromine

Abstract The magnetic moment of positive muons stopped in liquid bromine has been measured by determining the precession frequency in a magnetic field of sub ppm homogeneity with a stroboscopic method. The diamagnetic shielding of the magnetic field was determined by NMR measurements on analogous chemical compounds. The present result is μ μ / μ p = 3.1833448 (29) (±0.9 ppm).

Anomalous temperature dependence in the depolarization rate of positive muons in pure niobium

Abstract The temperature dependence of the depolarization rate for positive muons implanted into a pure niobium crystal has a pronounced minimum in the vicinity of 20 K. The data show self-trapping of the muon at low temperature, and impurity limited diffusion at temperatures above 65 K.

Measurement of the field dependence (Knight shift) of the hyperfine field at a positive muon in ferromagnetic nickel

Abstract The dependence of the hyperfine field at an interstitial positive muon in ferromagnetic field has been measured at room temperature yielding a Knight Shift constant K = 0.0025 (3). This Knight shift is interpreted in terms of the Pauli spin paramagnetism of s-p band electrons.

Muon spin rotation studies at SIN

Recently the accelerator and the muon channel at SIN became operational. We report here on some of the first positive muon spin rotation experiments at SIN. The first experiment we discuss concerns the chemistry of muonium. We have observed for the first time a muonium or radical signal in pure water. Next, we discuss the application of the positive muon for the study of ferromagnetic metals and alloys. First measurements on a single crystal of iron around liquid helium temperature seem to indicate that at low temperature the muon does not diffuse. We further report on the first stroboscopic observation of the muon spin rotation which will allow one to take full advantage of the high stopping density at SIN.