Hydrogen plasma characterization in an ECR based large volume plasma source under different cusp magnetic field topologies

Bibekananda Naik¹, S Sharma¹, R Narayanan¹, D Sahu¹, M Bandyopadhyay^2,3, A Chakraborty²,
M J Singh^2,3, R D Tarey¹ and A Ganguli^1
1Indian Institute of Technology Delhi, Hauz Khas, New Delhi, Delhi-110 016, India
²Institute for Plasma Research, Gandhinagar- 382 428, Gujarat, India
³Homi Bhabha National Institute, Mumbai, Maharashtra 400 094, India

Dedicated to Prof P K Kaw

The tautomerism of 5-fluorouracil (5-FU) was investigated in the gas phase and in solution. In the present work seven tautomers of 5-FU have been predicted and optimized. Six of them are related to those of uracils molecule, with the same stability order. Solvent effects were considered using a variable number (1-10) of explicit water molecules surrounding 5-FU in order to simulate the first hydration shell. More than 100 cluster structures with water were analyzed. Attachment of a fluorine atom changes the relative free energy order of uracil tautomers in the gas phase and in solution. For cases where literature data are available, the computed values were in good agreement with previous experimental and theoretical studies. Depending on the nature of the tautomers, cyclic, distributed water molecules, or clustered structures are formed. The hydration energies of various tautomers are large and vary dramatically between tautomers. The microhydrated environment stabilizes remarkably the enol forms more than the canonical keto one, although this one continues being the most stable. Several general conclusions were underlined. © Anita Publications. All rights reserved.
Doi: 10.54955/AJP.34.3-4.2025.211-222
Keywords: 5_Fluorouracil, Magnetic confinement, Large volume plasmas, ECR plasma,,  Langmuir probe.

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Method: Single- anonymous; Screened for Plagiarism? Yes
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