Rotational spectroscopy (ROT) is a powerful technique that, thanks to its intrinsic high resolution and high sensitivity, allows for accurately characterizing stable and transient species (ions, radicals, neutral molecules and clusters) in the gas phase and deriving information on their molecular structures and dynamics, information that hardly accessible from other experimental techniques. However, the task of extracting the aforementioned information, which starts with inverting the spectral observables, i.e., with the assignment of rotational transitions to an effective Hamiltonian, is challenging, time-consuming, and prone to errors. The availability of different kinds of microwave spectrometers (Frequency modulated spectrometers, Chirped-pulsed Fourier Transform, Pulsed-jet Fourier Transform etc.) and different gas phase generating systems (laser ablation, electric discharge, heating systems, pyrolysis etc.) makes it possible to investigate a large variety of molecules and/or clusters, which have, among the others, chemical, biological, and astrochemical interest.

To speed up and facilitate spectral assignment procedures, quantum-chemical calculations are essential; therefore, an intimate link between theory and experiment is unavoidable. In this respect,the VMS-ROT module of the VMS-DRAW graphical user interface is the most suitable tool to simulate, interpret and assign a rotational spectrum, because it is actually based on the interplay of theory and experiment, also enabling the user to easily deal with different microwave techniques.

NOTE: 64-bit SPFIT/SPCAT executables are available from HERE

Video Tutorials

How to simulate a rotational spectrum from calculations

Assignment and fitting of rotational spectra

Using VMS Peak Analyzer

VMS Doppler Splitting Tool for PJ-FTMW