Preparation And Research Of Nuclear Spin Singlet States

With the development of liquid nuclear magnetic resonance?NMR?technology,thousands of radio frequency pulse sequences and their combination pulse technologies are applied to various kinds of liquid nuclear magnetic resonance experiments.Despite their variety,all the time span of all these pulse sequence technologies are limited by the longitudinal relaxation time constant T₁.Recently,many research groups have successively put forward that there is a special nuclear spin-long-lived singlet states.The singlet state lifetime T_S is much longer than the spin longitudinal relaxation time T₁.Benefiting from the advantage of long spin memory,it has been successfully used in many fields.In this work,we have achieved the long-lived singlet states with two weakly coupled pairs of 2-chloroacrylonitrile firstly.On that basis,it is found that there are many different singlet states with various proportional coefficient combinations in the three-spin systems theoretically.Then the NMR singlet states experiments have been demonstrated that the diversiform singlet states have different lifetimes in acrylic spin systems.At the same time,in order to study the relaxation of long-lived singlets,we have explored the effect of temperature on the singlet states lifetimes.