Wigner D-matrix

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The Wigner D-matrix (also known as the Wigner rotation matrix) is a square matrix, of dimension 2j + 1, given by (Ref. 2 Eq. 4.12)

D^j_{m'm}(\alpha,\beta,\gamma) := \langle jm' | \mathcal{R}(\alpha,\beta,\gamma)| jm \rangle = e^{-im'\alpha } d^j_{m'm}(\beta)e^{-i m\gamma}

where \alpha, \; \beta, and \gamma\; are Euler angles, and where d^j_{m'm}(\beta), known as Wigner's reduced d-matrix, is given by (Ref. 2 Eq. 4.11 and 4.13)

\begin{array}{lcl} d^j_{m'm}(\beta) &=& D^j_{m'm}(0,\beta,0) \\ &=& \langle jm' |e^{-i\beta j_y} | jm \rangle\\ &=& [(j+m)!(j-m)!(j+m')!(j-m')!]^{1/2} \sum_\chi \frac{(-1)^{\chi}}{(j-m'-\chi)!(j+m-\chi)!(\chi+m'-m)!\chi!} \\ &&\times \left(\cos\frac{\beta}{2}\right)^{2j+m-m'-2\chi}\left(-\sin\frac{\beta}{2}\right)^{m'-m+2\chi} \end{array}

This represents a rotation of β about the (inital frame) Y axis.

[edit] Relation with spherical harmonic functions

The D-matrix elements with second index equal to zero, are proportional to spherical harmonics (normalized to unity)

D^{\ell}_{m 0}(\alpha,\beta,\gamma)^* = \sqrt{\frac{4\pi}{2\ell+1}} Y_{\ell}^m (\beta, \alpha )

[edit] External links

[edit] References

  1. Eugene Paul Wigner "Gruppentheorie und ihre Anwendungen auf die Quantenmechanik der Atomspektren", Vieweg Verlag, Braunschweig (1931).
  2. M. E. Rose "Elementary theory of angular momentum", John Wiley & Sons (1967)
  3. Miguel A. Blanco, M. Flórez and M. Bermejo "Evaluation of the rotation matrices in the basis of real spherical harmonics", Journal of Molecular Structure: THEOCHEM 419 pp. 19-27 (1997)
  4. Holger Dachsel "Fast and accurate determination of the Wigner rotation matrices in the fast multipole method", Journal of Chemical Physics 124 144115 (2006)
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