Moreover, it is important to realize that, between the maser pulses, the detected signal, although weak, is never below the noise in these experiments. This is shown in This suggests that in this sequence, maser bursts are not triggered by noise, but by persistent coherent in-plane magnetization that persists throughout the experiment. It is worth mentioning the orders of magnitude of the time scales involved in these experiments. Indeed, not only the maser pulses were separated by delays on the order of the second, but also their duration were on the order of ∼ 200 ms, as shown in Fig. . As mentioned above, the first maser was shorter, with a total duration of ∼ 50 ms (see Figure ). Therefore, applying a Fourier transformation to the decaying part of the pulse, one obtains an narrow line. This is exemplified by the spectrum obtained after processing the maser pulse occurring around 2.3 s in Figure . The obtained line width is ∼ 10 Hz, a rather unusual value for a non rotating solid (Fig. , and significantly smaller than the dipolar line width.