The Art of Long-Lived Nuclear Spin Order: Methods and Applications
In session 31 held on 20th July 2021, Dr. Mohamed Sabba gave a talk on "The Art of Long-Lived Nuclear Spin Order: Methods and Applications", via Zoom. The video was recorded live during the presentation and serves as an educative lecture.
Bio:
BSc at University of Greenwich with Prof. Jeremy Everett 2014-2017
PhD at University of Southampton with Prof. Malcolm Levitt 2017-2021
Postdoc with Prof. Malcolm Levitt 2021-
Follow Dr. Sabba:
Twitter: @ma_sabba
Research Gate: https://www.researchgate.net/profile/...
Abstract:
All physical systems are bound by entropy. In particular, nuclear spin order undergoes relaxation through several distinct modes. The cases of the relaxation of longitudinal and transverse order, characterized by the familiar time constants T1 and T2, are textbook examples in the field of liquid-state NMR which are routinely probed and fairly well-studied. For many years it was popularly believed that T1 was the ultimate upper bound on experimentally accessible relaxation times.
However, in coupled spin systems, it is possible to access a range of interesting configurations which had been almost completely overlooked in the formative decades of magnetic resonance. These configurations have often been organized under the loose umbrella term "long-lived nuclear spin order" owing to their exceptional lifetimes. The most prominent of these is nuclear singlet order which our group in 2004 demonstrated could be accessed easily in 2-spin-1/2 systems from ordinary room-temperature magnetization via simple pulse sequences. Since then the field has grown rapidly with insightful contributions from several excellent groups. There have been striking discoveries, such as room-temperature solution-state lifetimes beyond 1 hour in certain spin systems, which is orders of magnitude larger than T1 in the same conditions.
This talk will be an attempt at summarizing the basic theory and practice of generating, preserving, and reading out long-lived spin order in 2-spin-1/2 systems, with a pragmatic focus tailored towards the experimental spectroscopists curious in these techniques, as well as chemists interested in probing the dynamical properties of their molecules through the potentially unique and symmetry-sensitive relaxometry of long-lived order. We hope to portray this subfield of NMR as readily available rather than exotic and inscrutable. We discuss seminal experiments of the field and also present some of our recent experimental results on robust, highly efficient pulse sequences for accessing 2-spin-1/2 long-lived order in a wide range of chemical inequivalence regimes.