Optical Heteronuclear Spin Singlet Order Generation In Liquids At Room Temperature

Singlet order of nuclear spin pair has the characteristic of long life and is extremely useful in tracking slow chemical and biological processes.It has been widely used in hyperpolarized storage and sensing applications,as well as in the study of molecular conformational changes and spatial dif-fusion.The hyperpolarization storage of nuclear spin through the singlet order can effectively extend the life time of the system and expand the po-tential application of nuclear magnetic resonance spectroscopy.Recently,both homonuclear and heteronuclear nuclear spin singlet order have been realized in experiments,and the hyperpolarization of homonuclear nuclear spin singlet order has also been demonstrated in some relevant studies.Nev-ertheless,there is no hyperpolarized heteronuclear singlet order presented as we know.In addition,the hyperpolarization of nuclear spin achieved by the utilization of electron spin hyperpolarization requires a low temperature and an ultrastrong magnetic field.In this case,the value of the hyperpo-larizability can be obtained as p~2/3,which is usually much smaller than the polarizability p obtained by the nuclear spin itself.In this thesis,we use the optical hyperpolarization of the nitrogen-vacancy(NV)centers in nanodiamonds to achieve hyperpolarized heteronu-clear singlet order.Due to the NV centers'excellent optical properties at room temperature and the long coherence time of its electron spin,it has been regarded as the hope of nuclear spin hyperpolarization.Considering the formic acid(13CHOOH)solution of the liquid sample,we find that when the optical polarization of the NV centers is transferred to the13C or1H nu-clear spin pairs,13C and1H will show a larger hyperpolarization difference.By adiabatically decreasing the magnetic field,the hyperpolarization of the heteronuclear spin singlet order in the strongly coupled13C-1H pairs in the optical preparation of formic acid solution can yield a hyperpolarizability ap-proximately equal to p/3,which is an order of magnitude close to the nuclear spin itself the achievable polarizability p.In this thesis,we first propose the hyperpolarization scheme for a heteronuclear singlet order,which can real-ize a high polarization.Particularly,this scheme can be performed at room temperature and dose not require an ultrastrong magnetic field.The thesis consists of four chapters:In the first chapter,we introduce the relevant principles of nuclear mag-netic resonance,the singlet and singlet order of nuclear spin pairs,and NV centers system.In the second chapter,we discuss the nuclear spin hyperpolarization of solid sample and liquid sample.In solid sample,we utilize a single NV center for hyperpolarization,while in liquid sample,we use nano-diamonds to prepare nuclear spin hyperpolarization.In the third chapter,we investigate the hyperpolarization of the nuclear spin singlet order in the case of heteronuclear nuclei.Firstly,we obtain the hyperpolarization difference of the13C-1H spin pairs at B=0.36 T.With the magnetic field being adjusted to low field,the high-field eigenstates are adiabatically transformed into the nuclear singlet and triplet energy eigen-states in the low magnetic field.Then in the low field,the nuclear spin singlet order hyperpolarization can be prepared.In the fourth chapter,we summarize this thesis and look forward to the future work in this field.