Dynamical, energetic and entropic aspects of the fragmentation of excited neutral and cationic furan molecules in the gas phase
The aim of this Short Term Scientific Mission within the COST XLIC Action was to continue our collaborative study on the fragmentation of small ring molecule: furan (C4H4O). Furan belongs to the family of ring structures that are analogous to the deoxyribose building block of the DNA helix; hence it can serve as model system for track simulations in biological medium. The fragmentation mechanism of going through various intermediates is still unclear, so in this work our goal is to extend and complement previous studies.
Firstly, we investigated possible isomerization and dehydrogenation of furan by exploration of the appropriate regions in the potential energy surface with Density Functional Theory. In order to improve the description of the process, we applied a statistical approach that allows to describe the unimolecular decomposition of excited systems: M3C (Microcanonical Metropolis Monte Carlo). With the new 2.0 version of the M3C program we performed multiple simulations. In Figure 1 we present the probability of the most populated species as a function of the internal energy. In accordance with the results of previous pyrolysis experiments, the major observed products were the following species: CO, H3C4, H2C2 and H2C2O. Additionally, we note the constantly high probability of CO production for higher energies (purple line in Figure 1). This result is consistent with our previous calculations using ADMP molecular dynamics method. In conclusion, the improved M3C code has the capacity to become a convenient tool for the description of fragmentation processes.
We are currently working on a manuscript describing the obtained results that we plan to submit to the special issue of the PCCP journal devoted to the XLIC-COST Action. We also intend to continue the collaboration between the groups in Gdańsk and Madrid by extending the applied methodology to charged furan. These results will be useful to help in the interpretation of recent experimental measurements carried out by other groups in the XLIC network.
Figure 1 M3C results: Species probabilities as a function of the internal energy