Separation of the Ortho and Para NMR Signals in Solid Deuterium via DQ Filtering

✍ Scribed by Pekka Malmi; Matti Punkkinen; Eero Ylinen; Valeri Shevtsov

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 115 KB
• Volume: 145
• Category: Article
• ISSN: 1090-7807
• DOI: 10.1006/jmre.2000.2094

✦ Synopsis

Double quantum (DQ) filtering is shown to lead to an effective separation of the NMR signals from the para (I = 1) and ortho (I = 2) molecules in solid deuterium. The separation is achieved by the pulse sequence 90(φ)( degrees )-t(pr)-90(φ)( degrees )-t(ev)-90(x)( degrees )-t, where the phase-cycled first two pulses create the DQ coherence. Two components are observed after the third pulse; the para signal shows the maximum at a short time t while the ortho signal reaches the maximum at a longer t. The observed signal can be expressed as (1/2) summation operator(I) [F(I)(t(pr) - t) - F(I)(t(pr) + t)], where F(I)(t) is a proper fitting function for the free induction signal of the para and ortho molecules (with I = 1 or 2, respectively). Numerical fits to experimental data at 4.2 and 2 K show that this method can be used to determine the ratio F(1)(0)/F(2)(0) and thus, because the initial value F(I)(0) is proportional to the respective magnetization before the pulse sequence, the ortho and para concentrations in solid deuterium. Copyright 2000 Academic Press.