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Proton magnetic resonance in methane and its deuterated modifications Sandhu, Harbhajan Singh

Abstract

Proton magnetic resonance has been studied in methane and its deuterated modifications. Measurements of relaxation time were carried out at a frequency of 30 Mc/sec. using pulse techniques. The spin-lattice relaxation time has been measured in liquid and solid samples of CH₄, CH₃D, CH₂D₂ and CHD₃ between 110°K to 56°K. The simplest possible interpretation of our results in both the liquids and solids is that only one mechanism, that associated with the inter-molecular interactions, is probably predominant in causing relaxation. The spin-rotational and intra-molecular dipolar interactions do not seem to contribute appreciably to relaxation. The effect of dissolved paramagnetic ions has also been studied in samples of CH₄ between 110°K - 78°K and we have developed a very simple and reliable technique for obtaining oxygen-free samples in order to study T₁ in pure samples because T₁ has been found by us to be very sensitive to small, amounts of oxygen. The results verify the invers proportionality of T₁ to the oxygen concentration. The spin-spin relaxation time T₂ has been measured in liquid and solid samples between 110°K and 56°K. The results show that the line shape is predominantly due to inter-molecular interactions. Furthermore the resonance line has a gaussian shape at temperatures below 65°K and changes to a Lorentzlan shape at higher temperatures.

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