Ultrafast Vibrational Dynamics and Energy Transfer in Imidazolium Ionic Liquids

Mahesh Namboodiri, Mehdi Mohammad Kazemi, Tahir Zeb Khan, Arnulf Materny, Johannes Kiefer

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)


Femtosecond time-resolved coherent anti-Stokes Raman scattering (CARS) is used as a probe for monitoring the vibrational dynamics of room temperature ionic liquids (ILs). The experiments are performed on a series of 1,3-dialkylimidazolium ILs containing the bis(trifluoromethylsulfonyl)imide [NTf2] anion. The effect of methylation of the cationic C2 position on the dephasing time is studied analyzing [NTf2]-ILs of 1-ethyl-3-methylimidazohum [EMIM], 1-ethyl-2,3-dimethylimidazolium [EMMIM], 1-butyl-3-methylimidazolium [BMIM], and 1-butyl-2,3-dimethylimidazolium [BMMIM]. Raman coherences are excited around similar to 4400 cm(-1), and the vibrational dephasing of the modes in the fingerprint region is monitored as a function of time. The results indicate that vibrational energy transfer occurs governed by the interionic interactions. This is suggested by mode beating involving vibrations beyond the excitation spectrum as well as systematic differences in the temporal dephasing behavior. In contrast, the length of the cationic alkyl side chain has a negligible impact on the vibrational dynamics.
Original languageEnglish
Pages (from-to)6136-6141
Number of pages6
JournalJournal of the American Chemical Society
Issue number16
Publication statusPublished - 23 Apr 2014


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