The goal of the project is to develop a new methodology, termed gas modulation refractometry, GAMOR, and instrumentation based on this, for measuring refractivity, gas density and pressure with unprecedented precision and accuracy (in the sub ppm and low ppm region, respectively) and to develop primary standards. This means that we can develop a "Quantum gas density" and a "Quantum Pascal" as alternatives for future standards for the units.
The project is supported by the Swedish Research Council.
Refractometry constitutes an optical technique for assessment of refractivity, n-1, that also can assess molar density and gas pressure with high precision and accuracy. It has been anticipated that it could be used for assessment of pressure with a huge dynamic range, 1 mPa - 10 kPa, and with a precision and accuracy of 1 and 10 ppm (parts per million), respectively. However, this is far beyond what any existing instrumentation can achieve today.
The reason is that conventional refractometry suffers from a number of limitations caused by fluctuations and drifts. To remedy this, we have developed a novel laser-based methodology, GAs MOdulation Refractometry (GAMOR), that can alleviate such limitations.
It will be further developed so as to allow for the realization of instrumentation that can reach the aforementioned goals. To make this possible, novel modulation and characterization procedures will be developed that will eliminate the influence of pressure-induced cavity deformation that often is the limiting factor in conventional refractometry. This will allow for assessments solely limited by the accuracy of the molar polarizabilities of two gases (He and N2), which typically are in the low ppm range.
This would make the systems calibration-free, which will open up for a number of applications, including serving as primary standards for both molar density and pressure, i.e. so as to realize both the “Quantum Molar Density” and the “Quantum Pascal” entities.