Statistical Analysis of NMR Proton Spin-Lattice Relaxation Rates Measured at Various Pulse Repetition Times

Abstract

In this work, taking into consideration waiting time(WT) in successive automatic measurement, the effect of pulse repetition time(T_R) on spin-lattice relaxation time (T₁) was studied by a FT-NMR spectrometer. Inversion-recovery pulse sequence 180°τ-90°(FID)+T_R +WT was successively applied for a set of 10 different τ. T₁ was calculated from non-linear estimation of inversion recovery formula, using partially relaxed recovery signals corresponding to different τ. Holding WT constant, T_R was set at 6 diferent values, ranging from nearly 6T₁ to 0.7T₁. T₁ measurements were repeated 20 times for each T_R. For comparison T₁ measurements were also repeated by the null method. Data showed that the intensity of recovery signals after total waiting (T_R+WT) has the same value for all T_Rs and comparison of T₁ groups corresponding to these T_Rs indicates no significant difference among T₁ values measured(p>0.2). Keeping T_R+WT>5T₁, to reduce T_R more causes an imperfect signal. The results suggest that WT makes possible the use of a T_R shorter than 5T₁ and saves experimental time.

Key Words:

• NMR T1
• Pulse Repetition Times
• Inversion Recovery
• Non-linear estimation