title: Efficient rotational echo double resonance recoupling of a spin-1/2 and a quadrupolar spin at high spinning rates and weak irradiation fields.
abstract: A modification of the rotational echo (adiabatic passage) double resonance experiments, which allows recoupling of the dipolar interaction between a spin-1/2 and a half integer quadrupolar spin is proposed. We demonstrate efficient and uniform recoupling at high spinning rates (nu(r)), low radio-frequency (RF) irradiation fields (nu(1)), and high values of the quadrupolar interaction (nu(q)) that correspond to values of alpha=nu(1)(2)/nu(q)nu(r), the adiabaticity parameter, which are down to less than 10% of the traditional adiabaticity limit for a spin-5/2 (alpha=0.55). The low-alpha rotational echo double resonance curve is obtained when the pulse on the quadrupolar nucleus is extended to full two rotor periods and beyond. For protons (spin-1/2) and aluminum (spin-5/2) species in the zeolite SAPO-42, a dephasing curve, which is significantly better than the regular REAPDOR experiment (pulse length of one-third of the rotor period) is obtained for a spinning rate of 13 kHz and RF fields down to 10 and even 6 kHz. Under these conditions, alpha is estimated to be approximately 0.05 based on an average quadrupolar coupling in zeolites. Extensive simulations support our observations suggesting the method to be robust under a large range of experimental values.
authors.affiliation: School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv 69978, Tel Aviv, Israel.
authors.forename: Evgeny
authors.initials: E
authors.lastname: Nimerovsky
authors.forename: Amir
authors.initials: A
authors.lastname: Goldbourt
mesh_terms: D000465:Algorithms; D000535:Aluminum / Q000737:chemistry; D004574:Electromagnetic Fields; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011522:Protons; D011846:Radio Waves; D017641:Zeolites / Q000737:chemistry
chemical_list: D011522:Protons; D017641:Zeolites; D000535:Aluminum