Low-Cost, Balle-Flygare-Type Cavity Fourier Transform Microwave Spectrometer and Pure Rotational Spectroscopy Laboratory for Teaching Physical Chemistry and Astronomy


Few laboratory exercises exist that introduce undergraduate students to both the concepts and instrumentation used in rotational spectroscopy. Because of this gap in undergraduate laboratory training, a teaching laboratory for the pure rotational spectroscopy of benzonitrile has been developed and reported. Owing to benzonitrile's recent discovery in space, the molecular spectroscopic technique and target are applicable to both the physical chemistry and astronomy disciplines. Because of the size of the dipole moment and relative safety of the molecule chosen, the laboratory approach allows undergraduates to directly load, tune, measure, and assign spectra using the same quantum chemical approaches and spectroscopic assigning tools available to a researcher in the field. Concepts taught in this laboratory include the rigid and semirigid rotor, as well as low-level nuclear electric quadrupole coupling Hamiltonians. To minimize the budget and allow the students to get hands-on training with the rotational spectroscopy instrumentation, an interactive, low-cost, Balle-Flygare-type, cavity Fourier transform microwave (FTMW) spectrometer of research-grade quality was developed and is reported. Implementation of the laboratory exercise, time of exercise, and student response to the exercise is also reported.



Research Center/Lab(s)

Center for High Performance Computing Research


This material is based upon work supported by the National Science Foundation under Grant Nos. CHE-1841346 and CHE-2019072.

Keywords and Phrases

Hands-On Learning/Manipulatives; Physical Chemistry; Spectroscopy; Upper-Division Undergraduate

International Standard Serial Number (ISSN)

0021-9584; 1938-1328

Document Type

Article - Journal

Document Version


File Type





© 2021 American Chemical Society (ACS), All rights reserved.

Publication Date

09 Mar 2021