Hope Michael A, Björgvinsdóttir Snædís, Grey Clare P, Emsley Lyndon
Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland.
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
J Phys Chem Lett. 2021 Jan 14;12(1):345-349. doi: 10.1021/acs.jpclett.0c03457. Epub 2020 Dec 23.
In the raser effect, a sample spontaneously emits continuous radiofrequency radiation, allowing exceptionally narrow NMR line widths to be recorded without applying pulses. To achieve this phenomenon, a large negative magnetization must be induced, which we show here can be achieved for the O magnetization of isotopically labeled Gd-doped CeO using solid effect dynamic nuclear polarization (DNP), at high field and 110 K. This allows a 2 mHz line width to be measured, which is limited only by the magnetic field stability. The raser effect can be reversibly activated and deactivated by magic angle spinning (MAS), which modulates the nuclear spin coherence lifetime. The use of MAS DNP to enable the raser effect should be further applicable to other systems and nuclei.
在激射器效应中，样品自发地发射连续的射频辐射，从而能够在不施加脉冲的情况下记录异常窄的核磁共振线宽。为了实现这种现象，必须诱导出大的负磁化强度，我们在此表明，利用固体效应动态核极化（DNP），在高场和110 K的条件下，对于同位素标记的掺钆二氧化铈的O磁化强度可以实现这一点。这使得能够测量到2 mHz的线宽，该线宽仅受磁场稳定性的限制。激射器效应可以通过魔角旋转（MAS）可逆地激活和去激活，魔角旋转会调制核自旋相干寿命。利用MAS DNP实现激射器效应应该可以进一步应用于其他系统和原子核。
