IOP Publishing, Journal of Physics: Condensed Matter, 24(20), p. 244107, 2008
DOI: 10.1088/0953-8984/20/24/244107
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We report a study of the dynamic relaxation spectra of the ionic liquid 1-butyl-1-methylpyrrolidinium bis[oxalato]borate (BMP-BOB) by means of dielectric spectroscopy in wide temperature (123-300 K) and pressure (0.1-500 MPa) ranges. We find similar features to those observed in many conventional glass formers. The relaxation time of the primary relaxation taualpha strongly increases with applied pressure, while that of the secondary relaxation is almost insensitive to pressure. However, the shape of the primary relaxation at constant taualpha is the same whether the pressure is 0.1 or 500 MPa. Elevated pressure separates the secondary relaxation and makes possible the appearance of an excess wing on the high-frequency flank of the primary relaxation. Interestingly, the primitive relaxation time calculated by the coupling model falls in the range of the existence of the excess wing of BMP-BOB, suggesting an unresolved universal Johari-Goldstein beta-relaxation.