t1Noise and Sensitivity in Pulsed Field Gradient Experiments

In this paper, a calculation routine based on product operator formalism and coherence pathway is presented, which describes t1noise and sensitivity in pulsed field gradient experiments. Several examples including the absolute value mode pulsed field gradient COSY, MQF-COSY, MQC, HMQC, and NOESY sequences are investigated to study the t1noise stemming from the phase errors of radiofrequency (RF) pulses and the sensitivity affected by RF pulse rotation angles. Our theoretical results indicate that the t1noises in P-type COSY, multiple-quantum-filtered (MQF)-COSY, and multiple-quantum coherence (MQC) are lower than those in the N-type corresponding experiments, while in HMQC and NOESY there is no difference in t1noise effects between P-type and N-type spectra. Meanwhile, from the calculations, we obtained the optimized RF pulse rotation angles in those sequences. In MQF-COSY, an increase in sensitivity of about 4(cos2θ sinq−12θ)2− 1 (θ = arc cot can be achieved by using the optimized angles. In MQC, the increase is 2 cos2θ sinq−12θ − 1 (θ = arc cot . MQF-COSY experiments are also carried out to support our corresponding theoretical results.