All the 1H nuclei tend to show uniform T1 relaxation time in the same molecule at moderate MAS rate (<20 kHz), because of rapid 1H spin diffusion. However, this common belief breaks when the sample is spun at ultrafast MAS rate (>60 kHz). Each 1H nucleus may show individual T1 relaxation time. In such a case, the repetition time should be determined by the longest 1H T1 relaxation time, even if the other 1H nuclei have much shorter 1H T1 relaxation time. To solve this uncomfortable and inefficient situation, we mix the magnetization during repetition delay by RFDR. The RFDR sequence brings magnetization from quickly polarized 1Hs to slow 1Hs and reduces the optimal repetition time, leading to sensitivity enhancement.