Python control of a high-resolution near-infrared spectrometer for undergraduate use

Abstract

We describe a project designed to introduce senior undergraduate chemistry and physics majors to the use of more advanced laser spectroscopic techniques and the interpretation of spectroscopic line shapes. We present a spectrometer design comprising modular components that are controlled using a single Python program with a graphical user interface (GUI). Unlike commercial Fourier transform infrared spectrometers typically used in undergraduate laboratories, this instrument can measure much higher resolution (approximately 0.001 cm⁻¹ compared to 0.5 cm⁻¹) data, with significantly higher (10⁻⁴) fractional absorption sensitivity. The modular, open$-$table design allows for easy viewing of optical components and better understanding of the operation of the instrument. We demonstrate the functionality of the spectrometer by measuring the P(23) rotational-vibrational line of the ${\nu }_1+{\nu }_3$ combination band of acetylene at various pressures to extract a self-pressure broadening coefficient. An undergraduate laboratory assignment could also include estimating the Boltzmann constant from data for low pressure Doppler-broadened lines. An additional Python program with a GUI was built for user friendly least squares fitting of collected data. All Python codes developed are freely available on GitLab.