### Abstract

Inelastic or reactive collisions typically produce an anisotropic distribution of rotational angular momentum. An explicit and general treatment is given for the intensity and polarization of resonance fluorescence from molecules produced in such processes. Both classical and quantum results are expressed in terms of bipolar harmonics and state multipoles formed from linear combinations of density matrix elements. The treatment provides an inversion procedure for determining moments of the rotational angular momentum distribution; twelve independent moments can be obtained. The combinations of angular momentum operators involved are even in eight of these moments and odd in four, with respect to reflection in a plane containing the initial and final relative velocity vectors. Measurements of the even moments require linearly polarized excitation and fluorescence, whereas measurements of the odd moments require circularly polarized excitation. The requisite experimental geometry and other practical aspects are discussed. In the three appendices are discussed the classical limits of transition intensities, a density matrix treatment of atom-rigid-rotor collisions, including analysis of state multipole symmetries; and the coupling coefficients for parallel angular momenta.

Original language | English (US) |
---|---|

Pages (from-to) | 541-573 |

Number of pages | 33 |

Journal | Molecular Physics |

Volume | 35 |

Issue number | 2 |

DOIs | |

State | Published - Feb 1978 |

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### All Science Journal Classification (ASJC) codes

- Biophysics
- Molecular Biology
- Condensed Matter Physics
- Physical and Theoretical Chemistry

### Cite this

*Molecular Physics*,

*35*(2), 541-573. https://doi.org/10.1080/00268977800100391

}

*Molecular Physics*, vol. 35, no. 2, pp. 541-573. https://doi.org/10.1080/00268977800100391

**Angular momentum polarization in molecular collisions : Classical and quantum theory for measurements using resonance fluorescence.** / Case, D. A.; McClelland, G. M.; Herschbach, D. R.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Angular momentum polarization in molecular collisions

T2 - Classical and quantum theory for measurements using resonance fluorescence

AU - Case, D. A.

AU - McClelland, G. M.

AU - Herschbach, D. R.

PY - 1978/2

Y1 - 1978/2

N2 - Inelastic or reactive collisions typically produce an anisotropic distribution of rotational angular momentum. An explicit and general treatment is given for the intensity and polarization of resonance fluorescence from molecules produced in such processes. Both classical and quantum results are expressed in terms of bipolar harmonics and state multipoles formed from linear combinations of density matrix elements. The treatment provides an inversion procedure for determining moments of the rotational angular momentum distribution; twelve independent moments can be obtained. The combinations of angular momentum operators involved are even in eight of these moments and odd in four, with respect to reflection in a plane containing the initial and final relative velocity vectors. Measurements of the even moments require linearly polarized excitation and fluorescence, whereas measurements of the odd moments require circularly polarized excitation. The requisite experimental geometry and other practical aspects are discussed. In the three appendices are discussed the classical limits of transition intensities, a density matrix treatment of atom-rigid-rotor collisions, including analysis of state multipole symmetries; and the coupling coefficients for parallel angular momenta.

AB - Inelastic or reactive collisions typically produce an anisotropic distribution of rotational angular momentum. An explicit and general treatment is given for the intensity and polarization of resonance fluorescence from molecules produced in such processes. Both classical and quantum results are expressed in terms of bipolar harmonics and state multipoles formed from linear combinations of density matrix elements. The treatment provides an inversion procedure for determining moments of the rotational angular momentum distribution; twelve independent moments can be obtained. The combinations of angular momentum operators involved are even in eight of these moments and odd in four, with respect to reflection in a plane containing the initial and final relative velocity vectors. Measurements of the even moments require linearly polarized excitation and fluorescence, whereas measurements of the odd moments require circularly polarized excitation. The requisite experimental geometry and other practical aspects are discussed. In the three appendices are discussed the classical limits of transition intensities, a density matrix treatment of atom-rigid-rotor collisions, including analysis of state multipole symmetries; and the coupling coefficients for parallel angular momenta.

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U2 - 10.1080/00268977800100391

DO - 10.1080/00268977800100391

M3 - Article

AN - SCOPUS:0001215460

VL - 35

SP - 541

EP - 573

JO - Molecular Physics

JF - Molecular Physics

SN - 0026-8976

IS - 2

ER -