### Abstract

This paper concerns the theoretical improvement of the discrete dipole approximation (DDA) to provide scattering properties of clusters of spherical monomers. The first scattering coefficient (a1-term) in Mie theory is introduced to determine the dipole polarizability used in the DDA. In the a1-term method, a spherical monomer in the cluster is replaced by a single dipole. The accuracy of this method is tested to calculate extinction and scattering cross sections by a single sphere, two-touching spheres and three collinear touching spheres. It is found that when each monomer is replaced by a dipole the a1-term method is superior to the different types of DDA, e.g., the Lattice Dispersion Relation (LDR), at least for the target with the volume equivalent size parameter X, 0.2≤X≤2. This method also allows treatment of a relatively large sub-volume element which is replaced by a dipole, i.e. the size parameter of the monomer X_{m}~1.5. Furthermore, a great reduction in memory requirement and computing time are achieved, e.g. for two touching spheres the a1-term method requires only 6% of the total memory requirement and 0.008% of the total computing time for N=8448 with the LDR.

Original language | English |
---|---|

Pages (from-to) | 407-412 |

Number of pages | 6 |

Journal | Optical Review |

Volume | 2 |

Issue number | 6 |

DOIs | |

Publication status | Published - Jan 1 1995 |

Externally published | Yes |

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### All Science Journal Classification (ASJC) codes

- Atomic and Molecular Physics, and Optics

### Cite this

**Light scattering by clusters : The A1-term method.** / Okamoto, Hajime.

Research output: Contribution to journal › Article

*Optical Review*, vol. 2, no. 6, pp. 407-412. https://doi.org/10.1007/s10043-995-0407-1

}

TY - JOUR

T1 - Light scattering by clusters

T2 - The A1-term method

AU - Okamoto, Hajime

PY - 1995/1/1

Y1 - 1995/1/1

N2 - This paper concerns the theoretical improvement of the discrete dipole approximation (DDA) to provide scattering properties of clusters of spherical monomers. The first scattering coefficient (a1-term) in Mie theory is introduced to determine the dipole polarizability used in the DDA. In the a1-term method, a spherical monomer in the cluster is replaced by a single dipole. The accuracy of this method is tested to calculate extinction and scattering cross sections by a single sphere, two-touching spheres and three collinear touching spheres. It is found that when each monomer is replaced by a dipole the a1-term method is superior to the different types of DDA, e.g., the Lattice Dispersion Relation (LDR), at least for the target with the volume equivalent size parameter X, 0.2≤X≤2. This method also allows treatment of a relatively large sub-volume element which is replaced by a dipole, i.e. the size parameter of the monomer Xm~1.5. Furthermore, a great reduction in memory requirement and computing time are achieved, e.g. for two touching spheres the a1-term method requires only 6% of the total memory requirement and 0.008% of the total computing time for N=8448 with the LDR.

AB - This paper concerns the theoretical improvement of the discrete dipole approximation (DDA) to provide scattering properties of clusters of spherical monomers. The first scattering coefficient (a1-term) in Mie theory is introduced to determine the dipole polarizability used in the DDA. In the a1-term method, a spherical monomer in the cluster is replaced by a single dipole. The accuracy of this method is tested to calculate extinction and scattering cross sections by a single sphere, two-touching spheres and three collinear touching spheres. It is found that when each monomer is replaced by a dipole the a1-term method is superior to the different types of DDA, e.g., the Lattice Dispersion Relation (LDR), at least for the target with the volume equivalent size parameter X, 0.2≤X≤2. This method also allows treatment of a relatively large sub-volume element which is replaced by a dipole, i.e. the size parameter of the monomer Xm~1.5. Furthermore, a great reduction in memory requirement and computing time are achieved, e.g. for two touching spheres the a1-term method requires only 6% of the total memory requirement and 0.008% of the total computing time for N=8448 with the LDR.

UR - http://www.scopus.com/inward/record.url?scp=21844511678&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=21844511678&partnerID=8YFLogxK

U2 - 10.1007/s10043-995-0407-1

DO - 10.1007/s10043-995-0407-1

M3 - Article

VL - 2

SP - 407

EP - 412

JO - Optical Review

JF - Optical Review

SN - 1340-6000

IS - 6

ER -