Sketching the 75th International Symposium on Molecular Spectroscopy (ISMS) - Day 2
Olivia Wilkins
Day 2 of ISMS yielded 16 (!?!?) sketched talk summaries. Between yesterday’s 14 and today’s 16, no wonder I’m exhausted. Thirty talks in two days versus the 23 talks over an entire week of AAS is just wild. Phew.
Anyway, I was a bit all over the place on Day 2, but here are the talks I attended!
Rotational Structure/Frequencies (Session TD)
Microwave Spectroscopy of Isothiazole — Kaori Kobayashi (University of Toyama)
The first talk of the day talked about isothiazole, a ringed compound containing both a nitrogen atom and a sulphur atom. In general, ringed compounds are biologically important, and previous work was done on similar molecules that contained an oxygen atom instead of a sulphur. Among the vibrational modes studied were planar and nonplanar modes, shown on the right.
Extended Laboratory Investigation of the Pure Rotational Spectrum of the CH2CN Radical in the (Sub-)Millimeter Region (79-860 GHz) — Olivia Chitarra (Université Paris Saclay)
Astrochemical models are needed to predict astrochemically-relevant species, which in turn require characterized spectra. This is true for CH2CN, a radical species. Since this species is short-lived and cannot be procured commercially, it must be produced during experiments. In this work, CH2CN was produced by the reaction of CH3CN with a fluorine radical to yeild CH2CN and HF. CH2CN may seem simple, but it has a complex spectrum stemming from spit rotation, hyperfine structure on the nitrogen, and even more hyperfine structure! Improved parameters from this work enable future observational searches for this compound in the interstellar medium (ISM).
Electrical Discharge of Nitrogen Containing Molecules — Eva Gougola (DESY)
Nitrogen-containing heterocycles are found in meteorites and are biologically relevant as building blocks. But, are these compounds in the ISM? An electrical discharge experiment looked at species formed via electrical discharge interacting with nitrogen-bearing molecules. The molecules passed through two electrodes (one of which was a grounding electrode) before being super sonically expanded. Rotational spectra revealed a variety of compounds formed.
Vibrational Structure/Frequencies (Session TG)
Weakly-Bound Complex Formation between HCN and CH3Cl: A Matrix-Isolation and Computational Study — Emily Hockey (University of Maryland)
HCN is an astrochemically important molecule, and CH3CN is special because it is the first organohalogenated species detected in the interstellar medium. Both species were measured separately before being mixed. Comparing the three sets of spectra reveal a signature in the mixture from complexes that formed. There are several complex configuration candidates. Models were used to test which complexes were likely seen in the experiments.
Benchmarking (Session TB)
LaO Line List for the B2Σ+ – X2Σ+ Band System — Randika Dodangodage (Old Dominion University)
LaO is characteristic of S stars (which are types of M stars). Line lists, however, are needed to measure La abundances. Between the ground state (X2Σ+) and upper state (B2Σ+), the LaO spectrum has lots of splitting. In this work, 12,120 lines were assigned.
Rotational Structure/Frequencies (Session TD, continued)
Analysis of the High Resolution Rotational Spectrum of 2-Chloroethanol — Hayley Bunn (University of Wisconsin - Madison)
CH3Cl is the only organohalogen detected in the interstellar medium (ISM). This study looked at a more complex organohalogen: 2-chloromethanol. The gauche conformer (in which the angle between the Cl atom and the OH group is between 0 and 120 degrees) is the most stable, arising from a hydrogen-bonding relationship between the chlorine atom and hydroxyl group. The rotational spectrum of the molecule was collected between 140 and 700 GHz. Some more fits need to be done, after which there will be a search in space!
Fourier Transform Microwave Spectra of cis-3-Hexenal, trans-3-Hexenal, cis-2-Hexenal, and trans-2-Hexenal: Structural Isomers and Isomerization — Ryoto Ozawa (Sophia University)
For compounds like 3-hexanal, there is a relationship between structure and odor. The cis isomer (in which the two largest groups across a double bond are on the same side of that bond) smells like grass, whereas the trans isomer smells like tomatoes. A cavity-based Fourier transform microwave spectroscopic set-up involving a movable mirror inside a vacuum chamber was used to characterize the spectra of these species.
Deciphering the Complete Nuclear Quadrupole Coupling Tensor of Iodine with the Rotational Spectrum of 2-Iodoethanol — Michael J. Carrillo (Kent State University)
The 2-haloethanol species have been shown to prefer the gauche-gauche conformation in which hydrogen bonding between the OH group and the halogen stabilize the compound. Iodoethanol has not been studied previously. Interestingly, this work found that the trans-2-iodoethanol had a lower global energy when the OH group was flipped.
Centimeter-Wave Spectroscopy of Several New Silicon-Bearing Carbon Chains — Mike McCarthy (Center for Astrophysics ∣ Harvard & Smithsonian)
So far, 14 silicon-bearing compunds have been found in space. Silicon (Si) may contribute to dust formation (e.g., via Si2C). Experiments were conducted to build upon theory and looked at H2C3Si, HC3Si, H2CCSi, H2SiCC, HSiCCH, and two cyclic Si-containing compounds.
A High Speed Fitting Program for Rotational Spectroscopy — Brandon Carroll (Center for Astrophysics ∣ Harvard & Smithsonian)
Over time, new technology means faster data rates, which in turn means more data. Automated approaches are needed, and many of those already developed involve brute force and scaling. In this work, brute force was embraced (but made faster). The developed program is much faster than the Pickett suite but is limited to rigid rotors (or rigid-rotar-like calculations). See Carroll, Lee, and McCarthy (2021), or github.com/pbcarro.
Radicals (Session TN)
Extending Pure Rotational Measurements of the CH3O Radical Toward the Terahertz Domain — Marie-Aline Martin-Drumel (Unversité Paris Saclay)
The CH3O and CH2OH radicals are presumably important in the interstellar medium. In the lab, they are formed by hydrogen abstraction (which is not clean in that it produces other compounds as well) by reacting methanol (CH3OH) with fluorine (F). The products of this reaction are probed directly because they are short-lived. With this work, CH3O has now been experimentally measured up to 850 GHz (up from 400 GHz previously).
Improvements to New Program for Spin-Torsion-Rotation and the Methyl-Phenoxyl Radicals — Wes Westerfield (UC Davis)
Rotational transitions are relatively simple. On their own, spin states and torsion add complexities, which are even greater when combined. The program for calculating these effects was applied to meta methyl-phenoxyl (bottom left of the sketch). Computations still need adjustments but are underway.
Product-Specific Reaction Kinetics of CN with Propene Probed by Chirped-Pulse Fourier Transform Millimeterwave Spectroscopy — Divita Gupta (Rennes)
We expect that at low temperatures, the rate constant of a reaction become exceedingly slow. However, for some reactions, it has been found that rate constants increase at very low temperatures! The method used at Rennes to study such reactions combines CRESU and chirped-pulse techniques to look at reactions below 150 K. In this work, the reaction of CN and propene (C3H6) yielded vinyl cyanide (CH2CHCN).
Examining Methylamine Dissociation Products Using Theory and Rotational Spectroscopy: The CH2NH2 Radical — Connor Wright (UW-Madison)
The rotational and centrifugal distortion constants of CH2NH2 were predicted prior to experiments. So far, experiments have yielded 17 assigned transitions of this molecule. This is the first ever experimental detection of CH2NH2, at least in the microwave regime.
Plenary Special Session
The Urgent Need for Science and Innovation to Save this Warming Planet — Geraldine Richmond (U.S. Department of Energy)
A number of environmental-related topics can be studied with spectroscopy, including atmospheric studies, oil and water, nanodroplets, solar power, and polar ice. Currently, the Department of Energy has three initiatives where spectroscopy could be applied. Current “Energy Earthshots” and goals include hydrogen as an affordable fuel, long duration storage for renewable energy (10+ hours with a 90% cost reduction within a decade), and becoming carbon negative.
ISMS and NSF: Some History and a Look Forward — Fleming Crim (University of Wisconsin - Madison)
History
1939-1945: WWII
1945: Vannevar Bush proposes a national science foundation
1946: the precursor to ISMS begins at Ohio State
1950: NSF was created via the National Science Foundation Act
1957: Sputnik launch and the space race adds pressure
1960: donuts become a part of the symposium
1991: the name “International Symposium on Molecular Spectroscopy” was adopted
2014: ISMS was moved to the University of Illinois, Urbana-Champaign (UIUC)
Needs
A more diverse workforce because diverse ideas spark innovation
Increased financial support