Arijit Majumdar

All Publications

• A self-consistent analysis of cluster morphology in supercritical carbon dioxide from Small Angle X-ray Scattering CHEMICAL PHYSICS LETTERS Muhunthan, P., Majumdar, A., Younes, K., Vignat, G., Li, H., Rajkovic, I., Weiss, T., Sokaras, D., Ihme, M. 2025; 876

  View details for DOI 10.1016/j.cplett.2025.142190

  View details for Web of Science ID 001513620200002

• Supercritical Ethanol-CO2 Mixtures Exhibit Microscopic Immiscibility: A Combined Study Using X-ray Scattering and Molecular Dynamics Simulations. The journal of physical chemistry letters Fan, J., Yoon, T., Vignat, G., Li, H., Younes, K., Majumdar, A., Muhunthan, P., Sokaras, D., Weiss, T., Rajkovic, I., Ihme, M. 2025: 7090-7099

  Abstract

  Supercritical mixtures of ethanol (EtOH) and carbon dioxide (CO2) are classified as type-I mixtures, with complete macroscopic miscibility. However, differences in molecular polarity and interactions suggest a distinct phase behavior at the microscopic level. Here, we combine small angle X-ray scattering experiments and molecular dynamics (MD) simulations to investigate the microscopic structure of EtOH-CO2 mixtures under supercritical conditions. The structure factor exhibits nonlinear composition-dependent behavior, revealing pronounced local density fluctuations. The complementary MD simulations, using optimized force field parameters, provide atomistic insight, showing that EtOH forms self-associated, hydrogen-bonded aggregates, while CO2 remains more uniformly distributed. Cluster analysis identifies a preferential EtOH-rich composition exceeding the bulk average, governed by a balance between energetic and entropic competition. These results demonstrate that, contrary to macroscopic expectations, the mixture exhibits significant microscopic heterogeneity and immiscibility, which may influence solubility, reactivity, transport properties, and thermodynamic response functions. These findings challenge the conventional views of type-I fluids and emphasize the necessity of revising mixture states and considering molecular polarity.

  View details for DOI 10.1021/acs.jpclett.5c01293

  View details for PubMedID 40604336

• Direct observation of ultrafast cluster dynamics in supercritical carbon dioxide using X-ray Photon Correlation Spectroscopy. Nature communications Majumdar, A., Li, H., Muhunthan, P., Späh, A., Song, S., Sun, Y., Chollet, M., Sokaras, D., Zhu, D., Ihme, M. 2024; 15 (1): 10540

  Abstract

  Supercritical fluids exhibit distinct thermodynamic and transport properties, making them of particular interest for a wide range of scientific and engineering applications. These anomalous properties emerge from structural heterogeneities due to the formation of molecular clusters at conditions above the critical point. While the static behavior of these clusters and their effects on the thermodynamic response functions have been recognized, the relation between the ultrafast cluster dynamics and transport properties remains elusive. By measuring the intermediate scattering function in carbon dioxide at conditions near the critical point with X-ray photon correlation spectroscopy, we directly capture the cross-over dynamics between 4 and 13 picoseconds, revealing the transition between ballistic and diffusive motion. Complementary analysis using large-scale molecular dynamics simulations reveals that this behavior arises from collisions between unbound molecules and clusters. This study provides direct evidence of the ultrafast momentum exchange between clusters, which has significant impact on transport properties, solvation processes, and reaction kinetics in supercritical fluids.

  View details for DOI 10.1038/s41467-024-54782-1

  View details for PubMedID 39627208

  View details for PubMedCentralID PMC11615208

• Reaction nanoscopy of ion emission from sub-wavelength propanediol droplets. Nanophotonics (Berlin, Germany) Rosenberger, P., Dagar, R., Zhang, W., Majumdar, A., Neuhaus, M., Ihme, M., Bergues, B., Kling, M. F. 2023; 12 (10): 1823-1831

  Abstract

  Droplets provide unique opportunities for the investigation of laser-induced surface chemistry. Chemical reactions on the surface of charged droplets are ubiquitous in nature and can provide critical insight into more efficient processes for industrial chemical production. Here, we demonstrate the application of the reaction nanoscopy technique to strong-field ionized nanodroplets of propanediol (PDO). The technique's sensitivity to the near-field around the droplet allows for the in-situ characterization of the average droplet size and charge. The use of ultrashort laser pulses enables control of the amount of surface charge by the laser intensity. Moreover, we demonstrate the surface chemical sensitivity of reaction nanoscopy by comparing droplets of the isomers 1,2-PDO and 1,3-PDO in their ion emission and fragmentation channels. Referencing the ion yields to gas-phase data, we find an enhanced production of methyl cations from droplets of the 1,2-PDO isomer. Density functional theory simulations support that this enhancement is due to the alignment of 1,2-PDO molecules on the surface. The results pave the way towards spatio-temporal observations of charge dynamics and surface reactions on droplets.

  View details for DOI 10.1515/nanoph-2022-0714

  View details for PubMedID 39635141

  View details for PubMedCentralID PMC11501279

• Reaction nanoscopy of ion emission from sub-wavelength propanediol droplets NANOPHOTONICS Rosenberger, P., Dagar, R., Zhang, W., Majumdar, A., Neuhaus, M., Ihme, M., Bergues, B., Kling, M. F. 2023

  View details for DOI 10.1515/nanoph-2022-0714

  View details for Web of Science ID 000964452600001

• Regimes of evaporation and mixing behaviors of nanodroplets at transcritical conditions FUEL Ly, N., Majumdar, A., Ihme, M. 2023; 331

  View details for DOI 10.1016/j.fuel.2022.125870

  View details for Web of Science ID 000874538100008