New 2D spectroscopy methods

July 04, 2018

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy. Various methods are known in literature. But generally only the behaviour of a single excitation and its consequences are investigated.

Now physicists and chemists of Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany, have presented two novel principles of optical spectroscopy in the journal Nature Communications. Both approaches show new developments of the so-called coherent two-dimensional (2D) spectroscopy. In conventional 2D spectroscopy, scientists excite a system at a specific frequency and observe what happens at another frequency.

"Instead of starting with one excitation and analysing its dynamics, we here deploy two excitations into the same system and observe how they interact," says Professor Brixner, Head of the JMU Chair of Physical Chemistry I who is in charge of the research project at the University of Würzburg. This gives direct access, for example, to propagation phenomena (such as energy transport) because signals in the new method arise only if two initially separated excitations move and then meet.

The scientists illustrate the idea of "exciton-exciton-interaction-two-dimensional-(EEI2D)-spectroscopy" using a perylene bisimide-based J-aggregate. "J-aggregates are among the most important classes of supramolecular structures and the class of perylene bisimide dyes is ideally suited for such experiments," Professor Frank Würthner explains; he heads the JMU Chair of Organic Chemistry II and collaborates in the study.

This method is applicable to numerous physical, chemical, biological or engineering systems, for example, to decode dynamic properties such as energy transport of natural light-harvesting systems and artificial dye aggregates.

Investigating ionization with the 2D scheme

The physicists in Tobias Brixner's team conducted further research by combining coherent 2D spectroscopy with molecular beams "This has allowed us to investigate ionization with the 2D scheme for the first time," the professor explains. For this purpose, they used mass spectrometry instead of optical detection and obtained 2D spectra not only for the parent molecule but simultaneously also for all photoproducts.

"Our main challenge was the fact that particle densities in molecular beams are very low, rendering futile any previous conventional attempts at detecting coherently emitted four-wave-mixing signals," Brixner says. Instead, the researchers observed the ion generated by the sequence of excitation pulses, thereby merging two hitherto separate fields of research, namely 2D spectroscopy and mass spectrometry.

The physicists used the method exemplarily to identify the ionization pathways of 3d Rydberg states in nitrogen dioxide. In the future, this development will allow studying the influence of the environment on the coherent dynamics in larger molecules.

Both new approaches were developed within the scope of the research projects "Solar Technologies Go Hybrid" of DFG Research Unit 1809 and the ERC project "MULTISCOPE".

University of Würzburg

Related Mass Spectrometry Articles from Brightsurf:

Discovery of a new mass extinction
It's not often a new mass extinction is identified; after all, such events were so devastating they really stand out in the fossil record.

How vitamin C could help over 50s retain muscle mass
New research shows that vitamin C could help over 50s retain muscle mass in later life.

Oncotarget: Tumor markers for carcinoma identified by imaging mass spectrometry
Volume 11, Issue 28 of Oncotarget features 'Lipid and protein tumor markers for head and neck squamous cell carcinoma identified by imaging mass spectrometry' by Schmidt et, al. which reported that the authors used MALDI imaging mass spectrometry and immunohistochemistry to seek tumor-specific expression of proteins and lipids in HNSCC samples.

Nontargeted mass spectrometry reveals PFAS substitutes in New Jersey soils
Using a nontargeted mass-spectral approach, researchers identified the presence of chloro-perfluoro-polyether-carboxylate compounds (ClPFPECAs) in soils across the state of New Jersey.

Large-scale analysis of protein arginine methylation by mass spectrometry
In this research, the researchers offer an overview on state-of-the-art approaches for the high-confidence identification and accurate quantification of protein arginine methylation by high-resolution mass spectrometry methods, which comprise the development of both biochemical and bioinformatics methods.

Proximity of hospitals to mass shootings in US
Nontrauma center hospitals were the nearest hospitals to most of the mass shootings (five or more people injured or killed by a gun) that happened in the US in 2019.

Chemists use mass spectrometry tools to determine age of fingerprints
Chemists at Iowa State University may have solved a puzzle of forensic science: How do you determine the age of a fingerprint?

Keeping guns away from potential mass shooters
Researchers from Michigan State University measured the extent to which mass shootings are committed by domestic violence perpetrators, as well as identyifying how they illegally obtain guns, suggesting how firearm restrictions may prevent these tragedies.

Who is left behind in Mass Drug Administration?
Ensuring equity in the prevention of neglected tropical diseases (NTDs) is critical to reach NTD elimination goals as well as to inform Universal Health Coverage (UHC).

A mechanism capable of preserving muscle mass
By studying the young and aging muscles in mice, researchers from the Myology Research Center (Sorbonne Universite-Inserm) of the Institute of Myology identified a protein, CaVbeta1E that activates the factor GDF5.

Read More: Mass Spectrometry News and Mass Spectrometry Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to