Barbon Antonio, Rusetsky Grigory A, Linarello Sveva, Strzelczyk Roman, Fedaruk Ryhor
Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy.
Scientific-Practical Material Research Centre, Belarus National Academy of Sciences, 19 P. Brovka Str., Minsk 220072, Belarus.
J Magn Reson. 2024 Nov;368:107781. doi: 10.1016/j.jmr.2024.107781. Epub 2024 Sep 26.
Rabi oscillations (transient nutations) are a phenomenon that has proven itself well in EPR for identifying electron spin quantum numbers and electron-spin transitions. They are successfully applied when the Rabi frequency significantly exceeds the spin relaxation rates and therefore does not depend on these rates. However, the short transverse relaxation time, being comparable to or even shorter than the dead time of EPR spectrometers, makes it difficult to observe Rabi oscillations and their frequency depends not only on the intensity of the short microwave pulse, but also on its shape and relaxation rates. Two techniques are considered that are suitable for this case, in which Rabi oscillations are detected by monitoring the FID amplitude as a function of pulse duration or microwave field amplitude. We describe the FID-detected Rabi oscillations analytically or numerically for rectangular or shaped pulses, respectively. The description is confirmed by EPR experiments using DPPH as a model sample.
拉比振荡（瞬态章动）是一种在电子顺磁共振（EPR）中用于识别电子自旋量子数和电子自旋跃迁时已得到充分验证的现象。当拉比频率显著超过自旋弛豫率且因此不依赖于这些速率时，它们能成功应用。然而，短横向弛豫时间与EPR光谱仪的死时间相当甚至更短，这使得观察拉比振荡变得困难，并且其频率不仅取决于短微波脉冲的强度，还取决于其形状和弛豫率。考虑了两种适用于这种情况的技术，其中通过监测作为脉冲持续时间或微波场幅度函数的自由感应衰减（FID）幅度来检测拉比振荡。我们分别针对矩形脉冲或成形脉冲，通过解析或数值方法描述了FID检测到的拉比振荡。使用二苯基苦味酰基自由基（DPPH）作为模型样品的EPR实验证实了该描述。
