Preparation and Lifetime Studies of the Singlet State of Five Spins in Hexene Molecules Used to Guide the Preservation of the Parahydrogen-induced Nuclear Polarization State

Abstract

Parahydrogen-induced polarization (PHIP) technique can greatly enhance the sensitivity of nuclear magnetic resonance (NMR) signals, and has been applied in the fields of magnetic resonance imaging, in situ chemical reaction monitoring, etc. In addition to improving the sensitivity of different molecules in the PHIP, it is also crucial to extend and preserve the high polarization state. To achieve this, a possible approach is to transfer the polarized state into a nuclear spin singlet state. Here, we focus on the singlet states preparation in hexene molecule that can be polarized by PHIP. By designing optimal control pulses, a five-spin system in hexene molecule was manipulated, and various quantum states were prepared respectively. Our results show that three different nuclear spin singlet states could be prepared with the group CH2=CH- in hexene. The three different nuclear spin singlet states have longer lifetime than that of the initial state polarized by PHIP, and thus can be utilized as the intermediate states to delay the decay of the polarization state. By comparing the lifetime of the singlet state with the longitudinal relaxation time of the corresponding spin, it is deduced that converting the state of the polarized hexene to longitudinal magnetization may also be an effective way to preserve the polarizability.

Keywords

• parahydrogen-induced polarization (phip)
• nuclear magnetic resonance (nmr)
• nuclear spin singlet state
• optimal control pulse