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Speaker:
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Prof. Livio Gianfrani |
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Affiliation:
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Seconda Università di Napoli, Italy |
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Title:
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Physics: Towards a new definition of the Kelvin: Spectroscopic determination of the Boltzmann constant |
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Date:
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26-04-2007 |
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Start:
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16.00 |
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Location:
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FWN-Building 5111.0080 |
Abstract
Laser spectroscopy offers several effective and non-intrusive tools for temperature measurements in the gas phase. The most direct approach is based on determinations of the Doppler broadening effect in atomic or molecular transitions. This is a primary method for gas thermometry and the main advantage, compared to other methods that exploit electromagnetic radiation, consists in the fact that absolute radiation measurements are not required.
Recently, there has been a renewed interest in primary gas thermometry, because of the need of new determinations of the Boltzmann constant.
The unit of temperature, the Kelvin, is presently defined by the temperature of the triple point of water and, consequently, is linked to a material property. Instead, it would be advantageous to relate the unit to a fundamental constant, whose value should be fixed, similarly to what has been done for the speed of light and the unit of length. For the Kelvin, the corresponding constant is the Boltzmann constant. Nonetheless, in order to properly fix its value, the current value must be confirmed by several independent measurement methods, like acoustic or dielectric constant gas thermometry, or radiometric and spectroscopic methods.
I will report on the status of current research in precision molecular spectroscopy for highly
accurate determinations of the Boltzmann constant.
