In a weathered specimen, the stiff, tightly cross-linked, and/or oxidized fractions can be separated from the moderately cross-linked mobile regions and the fast-moving defects (in crosslinked rubbers these are the loops, dangling chain-ends, and sol fractions that are mechanically inelastic). In a T2 sense, rigid (possibly glassy) fractions formed due to shorter chain segments have a faster relaxation decay (shorter T2), whereas the others have slower relaxation decay (longer T2). The most constrained fractions, in this case, the regions closer to the irradiated surface, are associated with a rigid-limit coupling between the protons as high as about 30 kHz. (by a single 90° pulse) alone leads to underestimated results due to a loss in the initial decay signal owing to a longer receiver dead time (RDT, see Figure ). It is 11 µs for the low-field spectrometer used in these studies. The loss in the initial part of the signal can be compensated by performing the pulsed version of the magic-sandwich echo (MSE) experiment that performs a time-reversal by refocusing multispin dipolar interactions of the decay signal. The signals from both these experiments can be simultaneously fitted to obtain the relevant fractions and their respective transverse relaxation times. Slowly decaying components having relatively larger mobility are also probed by stitching a Hahn-echo signal to the FID. Figure illustrates this and the role of MSE-FID for NR and SBR weathered up to 988 h. A three-component fitting function is required to completely gauge these samples. Due to the higher number of data points obtained in an FID experiment, a 10 % weighting is applied. The three fractions obtained are: a rigid fraction due to tightly cross-linked or oxidized (due to weathering) regions, a second fraction that is representative of the majority of the vulcanizate's volume composed of relatively softer components of moderate cross-linking, and a third fraction consisting of the (mobile) defect fraction. A detailed discussion can be found in section 4.3.2.