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In particular for a massless particle the helicity is the same as the chirality while for an antiparticle they have opposite sign. The handedness in both chirality and helicity relate to the rotation of a particle while it proceeds in linear motion with reference to the human hands. The thumb of the hand points towards the direction of linear ...
A chiral phenomenon is one that is not identical to its mirror image (see the article on mathematical chirality).The spin of a particle may be used to define a handedness, or helicity, for that particle, which, in the case of a massless particle, is the same as chirality.
A further physical insight of optical chirality was offered in 2012; optical chirality is to the curl or time derivative of the electromagnetic field, what helicity, spin and related quantities are to the electromagnetic field itself. [6]
By contrast, for massive particles, distinct chirality states (e.g., as occur in the weak interaction charges) have both positive and negative helicity components, in ratios proportional to the mass of the particle. A treatment of the helicity of gravitational waves can be found in Weinberg. [5]
The chirality of a molecule that has a helical, propeller, or screw-shaped geometry is called helicity [5] or helical chirality. [6] [7] The screw axis or the D n, or C n principle symmetry axis is considered to be the axis of chirality. Some sources consider helical chirality to be a type of axial chirality, [7] and some do not.
Such optical activity due to extrinsic chirality was observed in the 1960s in liquid crystals. [28] [29] In 1950, Sergey Vavilov [30] predicted optical activity that depends on the intensity of light and the effect of nonlinear optical activity was observed in 1979 in lithium iodate crystals. [31] Optical activity is normally observed for ...
Many chiral molecules have point chirality, namely a single chiral stereogenic center that coincides with an atom. This stereogenic center usually has four or more bonds to different groups, and may be carbon (as in many biological molecules), phosphorus (as in many organophosphates ), silicon, or a metal (as in many chiral coordination ...
Bunn [8] predicted in 1945 that extrinsic 3d chirality would cause optical activity and the effect was later detected in liquid crystals. [9] [10] Extrinsic 3d chirality causes large optical activity and linear conversion dichroism in metamaterials. These effects are inherently tuneable by changing the relative orientation of incident wave and ...