Controlling the dynamics of quadrupolar spin‑1 nuclei by means of average Hamiltonian theory when irradiated with modified composite quadrupolar echo pulse sequences

The importance of the average Hamiltonian theory and its antecedent the Magnus expansion are discussed. The investigation of its convergence in different situations is very important. In this paper, we introduced a well-established approach to minimize the zeroth-order average Hamiltonian for modified composite pulse sequence in quadrupolar spectroscopy of spin-1. We designed two modified composite pulse sequences constructed by modifying the timing sequence in the original composite pulse sequences.¹⁷ We tested various configurations of times associated with the free evolution of the spin system in the modified composite pulses. We found that by decreasing the time delays between the pulses associated with the free evolution of spin system, the line shapes become increasingly better until we obtained the new modified composite pulses showing improvement of the signal compared to the original composite pulse sequences.¹⁷ This promising work is expected to play an important role not only for recording high resolution spectra of amino acids pharmaceutical samples and peptides but also for probing structural and dynamic information in biomolecules. The generality of the present theoretical scheme points to potential applications in solid-state NMR, to problems in chemical physics, quantum mechanics and theoretical developments, chemistry, and physical chemistry, and in interdisciplinary research areas whenever they include spin dynamics approach.