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Volume 130, Issue 21, 07 June 2009
In a previous paper [M. Carravetta and M. H. Levitt, J. Chem. Phys.122, 214505 (2005)], we presented the theory of long-lived nuclear spin singlet states in low magnetic field. In this paper, we consider the spin locking of long-lived singlet states in high magnetic field by the application of resonant radio frequency irradiation. We present theoretical results for unmodulated irradiation, including approximate analytical expressions for the singlet decay rate constants. We show the results of numerical simulations, which indicate that modulated radio frequency fields may be used to achieve broadband spin locking of singlet states but only in the case of a small difference in Larmor frequencies between the members of the spin pair.
130(2009); http://dx.doi.org/10.1063/1.3149802View Description Hide Description
Pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopy and supersonic cooling are used to investigate the torsional dynamics of the acetic acid cation and to determine an accurate value for the first adiabatic ionization potential of acetic acid, which has been the subject of debates for more than 40 yr. A doubling of the torsional barrier upon ionization is due to a significant shortening of the C–C bond and reduces the tunneling efficiency by an order of magnitude.