A Proposed Dynamic Pressure and Temperature Primary Standard.

Area of Science:

• Physics
• Spectroscopy
• Thermodynamics

Background:

• Diatomic gas molecules exhibit pressure-dependent vibrational frequencies and temperature-dependent rotational energy level populations.
• Laser spectroscopy can determine these spectral properties, enabling gas molecules to function as sensors.

Purpose of the Study:

• To investigate the potential of diatomic gas molecules as primary standards for dynamic pressure and temperature measurements.
• To understand the pressure and temperature dependence of molecular spectra under static conditions.

Main Methods:

• Utilizing laser spectroscopy to measure vibrational frequencies and rotational energy level populations.
• Employing coherent anti-Stokes Raman spectroscopy (CARS) for dynamic measurements.

Main Results:

• Spectra of selected molecules under static conditions are now understood regarding pressure and temperature effects.
• Feasibility studies indicate potential for measuring dynamic pressure up to 10^8 Pa and temperature up to 1500 K with 5% uncertainty.

Conclusions:

• Diatomic gas molecules are promising candidates for dynamic pressure and temperature primary standards due to rapid spectroscopic measurement capabilities.
• The temporal response is limited by molecular equilibration times, with CARS showing feasibility for high-pressure and high-temperature dynamic measurements.