USA As Represented by Secretary of the Navy

James P Yesinowski

Joel B Miller

Michael L Buess

Roy P Lindquist

Allen N Garroway

Allen M Garroway

Christopher A Klug

Edward A Hill

The invention relates to compounds known as 'optorelaxers,' for example, spin crossover (SCO) complexes that exhibit light-induced excited state spin trapping (LIESST) effects with transient unpaired electron spins, which are created (or destroyed) by varying the level and/or wavelength of light to which the complexes are exposed. Light conditions are used to switch the optorelaxers between transient paramagnetic and diamagnetic states to provide real-time control of Trelaxation in nuclear magnetic resonance (NMR) spectroscopy methods. The optorelaxers and methods of the invention provide increased detection sensitivity of NMR spectroscopy, with increased structural information content, while maintaining resolution for a wide variety of different NMR-active nuclei.

Optorelaxers for nuclear magnetic resonance spectroscopy

A method and apparatus for screening samples to determine which samples include a target material. Generally, the samples are pre-screened to determine which of the samples have a piezoelectric resonance when irradiated with an electric field, to thereby indicate the presence of the target material. The samples that have the piezoelectric resonance are then further screened by a different process to confirm the presence of the target material. For example, samples that have the piezoelectric resonance are further screened for a specific nuclear quadrupole resonance (NQR), a specific nuclear magnetic resonance (NMR) or a specific visual characteristic, to confirm the presence of the target material in the sample. The apparatus and method can be used, for example, to search luggage at ports of entry for the presence of cocaine hydrochloride or heroin hydrochloride.

Method and apparatus for detecting a target material in a sample by pre-screening the sample for piezoelectric resonance

Nuclear magnetic resonance analysis of powdery or other randomly oriented solid samples is improved by slowly rotating the sample with a period exceeding the nuclear spin relaxation time of nuclei in the sample. As a result, a relatively large proportion of the crystallites in the sample are brought into resonance, thereby improving the signal to noise ratio of the NMR reading. In addition, information about the width of the entire spectrum can be obtained from analysis of measurements of only a portion of it.

Apparatus and method for performing NMR spectroscopy on solid sample by

Acoustic ringing and adverse effects from variations in the NQR detection of explosives and narcotics are minimized or eliminated. A specimen is irradiated with a modified steady state steady state free precession (SSFP) pulse sequence which combines a phase-alternated pulse sequence (PAPS) with a non-phase-alternated pulse sequence (NPAPS). The resulting signals from the PAPS and NPAS may then be coadded to cancel out the FID contributions to the signals. By canceling out the FID contributions to the signals, the effects of probe ringing and other extraneous responses, as well as the effect of temperature variation, are minimized or removed. The present method is especially effective in the detection of explosives and narcotics having .sup.14 N or .sup.35,37 Cl nuclei. A steady state free precession pulse which is especially useful with the method of the present invention is the strong off-resonance comb (SORC). In another embodiment of the invention, the effects of probe ringing can also be minimized or removed by repeating the detection procedure at a frequency which is sufficiently off-resonance so that only frequency independent effects, such as probe-ringing, can be observed.

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Fort Washington, MD, United States of America

James P Yesinowski