Automated, context-free assignment of asymmetric rotor microwave spectra

Abstract

We present a new algorithm, Robust Automated Assignment of Rigid Rotors (RAARR), for assigning rotational spectra of asymmetric tops. The RAARR algorithm can automatically assign experimental spectra under a broad range of conditions, including spectra comprised of multiple mixture components, in ≲100 s. The RAARR algorithm exploits constraints placed by the conservation of energy to find sets of connected lines in an unassigned spectrum. The highly constrained structure of these sets eliminates all but a handful of plausible assignments for a given set, greatly reducing the number of potential assignments that must be evaluated. We successfully apply our algorithm to automatically assign 15 experimental spectra, including 5 previously unassigned species, without prior estimation of molecular rotational constants. In 9 of the 15 cases, the RAARR algorithm successfully assigns two or more mixture components.

The Role of Non‐Covalent Interactions on Cluster Formation: Pentamer, Hexamers and Heptamer of Difluoromethane

“…Hence, several automated methods had to be developed to analyze the data originated from the CP-FTMW due to the abundance of observable transitions in the spectra. [43][44][45] As described in an interesting paper by Watson, [46] asymptotic symmetric top limits are observed, producing in these large molecular systems regular 2C spacings, where C is the experimental rotational constant in the oblate limit. [47] For this reason, the fit procedure which we developed was focused on the search for these regular spacings and it was implemented through a Python script.…”

“…In summary, there are plenty of lines in all spectral regions and it is almost impossible to identify clear patterns of each cluster with traditional procedures. Hence, several automated methods had to be developed to analyze the data originated from the CP‐FTMW due to the abundance of observable transitions in the spectra [43–45] . As described in an interesting paper by Watson, [46] asymptotic symmetric top limits are observed, producing in these large molecular systems regular 2 C spacings, where C is the experimental rotational constant in the oblate limit [47] .…”

Testing the Scalability of the HS-AUTOFIT Tool in a High-Performance Computing Environment

“…This has raised the need for computer tools capable of automation and speedup of the analysis of such data. Some of the most used approaches in the field are based on genetic algorithms [13], assignment via non-linear spectroscopy [14,15], implementation of artificial neural networks [16], robust automated assignment of rigid rotors [17], and algorithms for a broad search that fit all possible combinations of a set of transitions (such as AUTOFIT) [4]. Below, we report some technical details of the mentioned techniques.…”

“…The robust automated assignment of rigid rotors (RAARR) algorithm [17] can rapidly assign the experimental rotational spectrum for a "near-rigid" asymmetric top even in a mixture of conformers. In the first version of RAARR, µ a and µ b (the permanent electric dipole moment components along the a and b inertial axes) type lines are required to be non-zero.…”

The Role of Non‐Covalent Interactions on Cluster Formation: Pentamer, Hexamers and Heptamer of Difluoromethane

“…Hence, several automated methods had to be developed to analyze the data originated from the CP‐FTMW due to the abundance of observable transitions in the spectra. [ 43 , 44 , 45 ] As described in an interesting paper by Watson, [46] asymptotic symmetric top limits are observed, producing in these large molecular systems regular 2 C spacings, where C is the experimental rotational constant in the oblate limit. [47] For this reason, the fit procedure which we developed was focused on the search for these regular spacings and it was implemented through a Python script.…”