Pal, Samanwita ; Chandrakumar, N. (2009) Study of dynamics in pentachlorophenol in the solid state by 1D Nuclear Quadrupole Resonance exchange spectroscopy Molecular Physics, 107 (14). pp. 1505-1511. ISSN 0026-8976
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Related URL: http://dx.doi.org/10.1080/00268970902950402
Abstract
The paper reports studies of the dynamic process in pentachlorophenol (PCP) in the solid state by one-dimensional Nuclear Quadrupole Resonance (NQR) exchange spectroscopy employing shaped rf pulses. Pentachlorophenol exhibits intramolecular hydrogen bonding between the hydroxyl proton and one of the o-chlorines. Reorientation of the hydrogen bond with migration of the hydroxyl proton from one o-chlorine to the other is possible in a wide temperature range. In this process the two o-chlorines are exchanged; at the same time this implies the exchange of the two m-chlorines as well, which we have chosen to monitor, modeling it as a two-site exchange process. A detailed analysis of the appropriate Bloch-McConnell equation is performed to formulate the relevant kinetic matrix. The exchange pulse sequence implemented by us involves suitably modulated shaped RF pulses to achieve simultaneous on-resonance excitation of the two exchanging sites. This approach results in a clear definition of the exchange time window and requires only a short experiment time. Kinetic parameters, namely, the spin-lattice relaxation rate and the exchange rate are deduced from the experimental signal intensities. Variable temperature measurements in the range 213 K-318 K have been carried out to extract the activation parameters as well.
Item Type: | Article |
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Source: | Copyright of this article belongs to Taylor and Francis Ltd. |
Keywords: | Proton Migration; Quadrupolar Nuclei; NQR Spectroscopy; Modulated Shaped Pulses; Simultaneous Excitation |
ID Code: | 5435 |
Deposited On: | 18 Oct 2010 09:40 |
Last Modified: | 16 May 2016 15:56 |
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