**Description**

The programme demonstrates two observable effects which arise out of the requirement that the two particle wave function must be anti symmetric under particle exchange for fermions or symmetric for bosons.

Module code and title: | SM351, Quantum theory and atomic structure |
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Item code: | SM351; 10 |

First transmission date: | 23-09-1974 |

Published: | 1974 |

Rights Statement: | |

Restrictions on use: | |

Duration: | 00:24:22 |

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Producer: | John Richmond |

Contributors: | Paul Clark; Allan Krass |

Publisher: | BBC Open University |

Keyword(s): | 3-D models; Atomic scattering experiments; Billiard ball experiment; Indistinguishability; Super fluid-helium experiment; Super-fluidity/conductivity |

Footage description: | Film shots of a super fluid helium fountain. Allan Krass introduces the programme. Shots of billiard balls in collision on a billiard table. These are used to model the way in which classical mechanics can distinguish between identical particles in collision An animated diagram is also used. The experiment is repeated using a stream of billiard balls to obtain a scattering effect. Krass shows a spherical model which demonstrates the random scattering effect expected by classical mechanics in 3 dimensions. Krass next shows a spherical model similar to the one above which shows the scatter of fermions. The scatter is not random, there being no events at 90C. Krass draws a graph which contrasts the scatter of fermions with classical scatter. Paul Clark explains why fermions avoid scattering at 90C. He uses several graphic aids His explanation is essentially mathematical. Allan Krass introduces part two of the programme. This examines identical spinless bosons which do not interact but have a high probability of being found near each other. Paul Clark, using captions and graphics, develops the quantum theory for a pair of identical particles in a one dimensional square well. He uses the wave functions for particles in the ground and first excited states and demonstrates how the position of the particle in the well is calculated. Allan Krass shows several 3 dimensional models which illustrate the resulting probability distribution. Several computer generated illustrations are also used. Paul Clark carries on with the mathematics. Allan Krass and Paul Clark demonstrate that non interacting bosons tend to follow each other about in the well. They use models and graphics to illustrate their points. Allan Krass sums up. He explains how the topics discussed lead up to an explanation of the super fluid helium fountain effect. The apparatus for this experiment is shown diagrammatically and explained. Film shots of a helium fountain. |

Master spool number: | 6HT/71435 |

Production number: | 00525_1147 |

Videofinder number: | 1050 |

Available to public: | no |