Production of Spin-Polarized Molecular Beams via Microwave or Infrared Rotational Excitation

Achieving high nuclear spin polarization in molecules is critical for enhancing the efficiency of nuclear fusion reactors and significantly boosting signals in nuclear magnetic resonance (NMR) and medical imaging. However, existing methods face substantial limitations in meeting the demand for large quantities of highly polarized molecules. Conventional techniques, including atomic beam sources, Stern-Gerlach separation, and spin-exchange optical pumping, are severely constrained by their microscopic production rates. Other approaches like Dynamic Nuclear Polarization (DNP) require the complex and costly removal of radicals, which is prohibitive for medical uses, while cryogenic cooling yields insufficient polarization levels and production rates for high-volume applications. These challenges in scalability, purity, and production rate hinder the widespread utility of spin-polarized molecules.

In this concept, highly nuclear spin-polarized small molecules are produced by exciting cold molecular beams with circularly polarized microwave or infrared (IR) radiation. The process begins by generating a high-flux molecular beam where molecules are cooled predominantly to their rotational ground state. These molecules are then selectively transferred to specific rovibrational states using techniques such as Stimulated Raman Adiabatic Passage (STIRAP) or π-pulses. Rotational polarization is subsequently transferred to nuclear spins via hyperfine interactions, and these quantum beats are suppressed by applying a strong magnetic field or de-excitation. Finally, the polarized molecules are collected on cold surfaces. This direct intramolecular polarization method, enabled by advances in high-power, tunable lasers and microwave amplifiers, achieves substantial production rates and high polarization levels, often over 90%, for a range of molecules including hydrogen isotopes like DT, as well as O₂, NO, N₂O, ¹³CO, and H₂S₂.

Applications

1. Nuclear Fusion Fuel Production: This invention provides a scalable method to produce the high quantities of spin-polarized tritium deuteride (DT) molecules needed to significantly increase the efficiency of future nuclear fusion reactors.

2. Enhanced Magnetic Resonance Applications: The technology enables the generation of highly spin-polarized small molecules, which can dramatically boost signal strength in both Nuclear Magnetic Resonance (NMR) for scientific analysis and Magnetic Resonance Imaging (MRI) for medical diagnostics.

3. Specialized Chemical Reagent Manufacturing: This invention allows for the high-volume production of various highly spin-polarized small molecules, which can be supplied as unique chemical reagents for advanced research, industrial processes, or specialized product development.

Advantages

1. Significantly Higher Production Rates: The invention projects production rates orders of magnitude greater than existing methods like Atomic Beam Sources (ABS), Stern-Gerlach spin-separation, and spin-exchange optical pumping, making it viable for practical fusion reactors and large-scale NMR applications.

2. Cleaner Production for Medical Applications: Unlike Dynamic Nuclear Polarization (DNP), which requires complex and costly removal of radicals for medical applications, this invention directly polarizes nuclear spins without the use of radicals, simplifying the process and improving purity for enhanced MRI.

3. Broader Molecular Applicability: The method is uniquely effective for polarizing non-symmetric hydrogen isotopes such as HD, DT, and HT, which have weak electric dipole moments and are challenging to polarize efficiently with existing approaches.

4. Superior Polarization Efficiency: The invention achieves polarization through rapid intramolecular hyperfine interactions, allowing for significantly higher molecular beam densities and larger beam areas compared to beam separation techniques like Stern-Gerlach, which are inherently limited by the physical separation process.