t(1) noise and sensitivity in pulsed field gradient experiments

In this paper, a calculation routine based on product operator formalism an d coherence pathway is presented, which describes t(1) noise and sensitivit y in pulsed field gradient experiments. Several examples including the abso lute value mode pulsed field gradient COSY, MQF-COSY, MQC, HMQC, and NOESY sequences are investigated to study the t(1) noise stemming from the phase errors of radiofrequency (RF) pulses and the sensitivity affected by RF pul se rotation angles. Our theoretical results indicate that the t(1) noises i n P-type COSY, multiple-quantum-filtered (MQF)-COSY, and multiple-quantum c oherence (MQC) are lower than those in the N-type corresponding experiments , while in HMQC and NOESY there is no difference in t(1) noise effects betw een P-type and N-type spectra, Meanwhile, from the calculations, we obtaine d the optimized RF pulse rotation angles in those sequences. In MQF-COSY, a n increase in sensitivity of about 4(cos(2)theta sin(q-1)2 theta)(2) - 1 (t heta = are cot root 2/(q-1)+1)can be achieved by using the optimized angles . In MQC, the increase is 2 cos(2)theta sin(q-1)2 theta - 1 (theta = are co t root 2/(q-1)+1). MQF-COSY experiments are also carried out to support our corresponding theoretical results. (C) 2000 Academic Press.