| 释义 |
Larmor Physics.|ˈlɑːmə(r)|
The name of Sir Joseph Larmor (1857–1942), Irish-born physicist, used attrib. and in the possessive with reference to a theorem enunciated by him in 1897, according to which the effect of a uniform magnetic field on a rotating particle is (to a first approximation) to cause the frame of reference in which the particle is rotating to rotate in turn about the direction of the magnetic flux with a frequency γB/2π (where γ is the magnetomechanical ratio and B the magnetic induction), which for an orbital electron in a monatomic molecule represents a precessional frequency of eB/4πm (e and m being the charge and mass of the electron); so Larmor frequency, Larmor precession; Larmor's theorem; also Larmor radius, the radius of the helical path of a free charged particle spiralling about magnetic field lines.
1923Larmor's theorem [see Coriolis]. 1926E. C. Stoner Magnetism & Atomic Struct. iv. 68 The Larmor precession is of great importance in the treatment of the Zeeman effect, this and diamagnetism being different aspects of the same phenomenon. 1951Physical Rev. LXXXIII. 1000/2 The Larmor frequency, ωp = 2µp H/ℏ, of a sample of protons in the magnetic field is measured by the resonance absorption method. 1957B. I. & B. Bleaney Electr. & Magn. viii. 186 As a consequence of the Larmor precession, each electron acquires a component of angular momentum about the direction of [the magnetic induction] B. 1962W. B. Thompson Introd. Plasma Physics vii. 151 In a magnetic field a second length becomes important, the Larmor radius, rL, i.e. the radius of the circle formed by the particle orbit about the magnetic field lines. 1971D. W. Sciama Mod. Cosmol. ii. 36 The galactic magnetic field thus has an important effect on the motion of cosmic rays if their Larmor radius is substantially less than the size of the Galaxy. |