No description available.

The technique of electron-nuclear double resonance spectroscopy (ENDOR) has been used to determine the identity and structure of radicals trapped in x-irradiated single crystals of cytosine monohydrate and caffeine hydrochloride dihydrate. The radical studied in cytosine mono-hydrate had previously been observed by several workers using electron paramagnetic resonance (EPR) but its identity was in question. All intramolecular and several intermolecular proton hyperfine couplings were analyzed in detail. The experimentally determined coupling parameters were compared with ones obtained by theoretical means for several possible radical species. The agreement between the observed and calculated parameters fit best for the radical formed by net addition of a hydrogen atom to 0(2) of cytosine, with the hydroxyl proton lying in the nodal plane of the π-system. The appearance of twice the number of certain ENDOR lines than expected from the crystal symmetry was interpreted by postulating that the radical was stabilized in two different conformations at 77°K. The assignment of the hyperfine couplings to specific protons was supported by an ENDOR study of a partially deuterated cytosine monohydrate crystal, grown from heavy water. Three different radical species were identified in caffeine hydrochloride dihydrate x-irradiated at room temperature. The EPR spectrum of this system, which had not previously been reported, was too complex to be analyzed. Furthermore, the EPR spectra of two of the radicals studied by ENDOR could not be distinguished in the overall EPR lineshape. One of these radicals had a lifetime of only a few hours and was tentatively identified as the methyl radical, primarily on the basis of the observed isotropic proton hyerpfine coupling constant of -62.65 MHz. The other radical was indefinitely stable and was identified as that formed by net abstraction of a hydrogen atom from N(9) of the caffeine moiety. This radical is equivalent to that which would be produced by the loss of an electron from a neutral caffeine molecule, the caffeine cation; as such, it is the first reported cation radical in a purine derivative. The radical which dominated the EPR spectrum was identified as that resulting from net addition of a hydrogen atom to C(8) of the protonated caffeine molecule. The identification of this radical was based on the analysis of four different proton hyperfine couplings. Nitrogen (¹⁴N) hyperfine and quadrupole coupling tensors were also obtained from the ENDOR spectra and were attributed to N(7). The observation of ¹⁴N-ENDOR lines, which had not previously been reported in any pyrimidine or purine derivative, provided a second, independent estimate of the unpaired spin density centred on N(7). An indirect second-order effect, giving rise to a non-crossing phenomenon, was observed between the methylene protons, which were also found to be non-equivalent. The structure of this radical was found to agree with those determined previously by EPR and by molecular orbital calculations for the analogous species in other purine derivatives. / Science, Faculty of / Chemistry, Department of / Graduate

[by] F. Bitter [and] J. Brossel. / No more published. / Bibliography: p. 24. / Army Signal Corps Contract No. W-36-039 sc-32037. Dept. of the Army Project No. 3-99-10-022.

The photodissociation dynamics of cyanogen iodide (ICN) in the A continuum was studied by the three-dimensional sliced fluorescence imaging (3DSFI) method. The fourth harmonic of a Nd:YAG laser (266 nm) was used to dissociate a low pressure (5 mTorr) sample of ICN, and the resulting CN photofragments were probed by optical-optical double resonance (OODR) detection scheme. A theoretical framework on the emitted fluorescence intensity has been developed to analyze the experimentally obtained image. The vector correlations among the ICN parent molecule transition dipole moment £g, the CN fragment recoil velocity v and the CN rotational angular moment J can be revealed.

The basic theories of Nuclear Quadrupole Resonance are outlined, together with some basic NMR theory and its application to double resonance techniques. An improved design of spectrometer using double resonance is presented, including a description of a new flow cryostat which can operate down to 4.2°K with low (250 cc/hour) consumption of liquid He. The whole apparatus may be used to detect NQR signals in solids over the frequency range 100 kHz-5 MHz. The theory of double resonance with spin mixing by continuous coupling (D R CC) is developed and illustrated by experiments performed on HCOOD, HDO and several nitrogen-containing compounds, including Imidazole. Further experiments were then carried out on samples dilute in deuterium, including the detection of NQR in formic acid (HCOOH) due to naturally abundant deuterium. Other experiments on proton-deuteron interactions in amide groups and in water molecules are also described and compared with results previously published on fully-deuterated amides and D₂0 as a water of crystallisation in L-serine hydrate. The NQR spectrum of Lanthanum Nicotinate Dihydrate is obtained using F.M. techniques and related to its structure. The theory of Zeeman NQR in spin 3/2 nuclei is developed with reference to the double resonance technique, and the measured quadrupole coupling constants of ²³Na and ²D in NaOH and some of its hydrates are discussed. Finally, some standard theories concerning proton relaxation times in solids at low temperatures (4°K-300°K) are outlined and related to some, measured relaxation times, illustrating their significance to the double resonance technique. The concluding chapter outlines a speculative proposal for a new spectrometer design.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [115]-118).

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 1979 / Includes bibliographical references. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Chemistry

A técnica de dupla ressonância unidimensional para alta resolução em líquidos constitui o objetivo deste trabalho. Para isso construiu-se uma sonda de dupla ressonância, apropriada para experiências heteronucleares do tipo 13C-{1H}. Empregam-se algumas sequências de pulsos para permitir as medidas do EON e do desacoplamento nuclear entre 1H e 13C. Emprega-se o EON com a finalidade de obter um aumento na intensidade do sinal de RMN do 13C; emprega-se o desacoplamento para eliminar a estrutura fina que surge devido ao acoplamento nuclear entre 1H e 13C. Inclui-se uma breve revisão sobre a teoria com a fmalidade de unificar o tratamento desta com as aplicações. As técnicas experimentais são discutidas e alguns espectros são mostrados para ilustrar os principais resultados / The one dimensional double resonance technique for high resolition in liquids is the main purpose of this work. For this we have built a double resonance probe, suitable for heteronuclear 13C-{1H} experiment. Some pulse sequences are employed to allow the NOE and decoupling between 1H e 13C to be measured. The NOE is employed in order to obtain a three-fold enhancement of the 13C NMR signal; decoupling is employed to eliminate the fme structW\'e arising from spin coupling between 1H e 13C. A short review about theory is included to provide unified treatment with applications. The experimental techniques are discussed and some spectra are shown to illustrate the main results.

Adrian C. Melissinos. / "November 10, 1958." Reprinted from The physical review, vol. 115, no. 1, pp. 126-129, July 1, 1959." / Includes bibliographical references. / Army Signal Corps Contract DA36-039-sc-78108. Dept. of the Army Task 3-99-20-001 and Project 3-99-00-000.

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xi, 124 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 81-87).