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Identifier

000433140

Title

Ultrahigh-density spin-polarized Hydrogen isotopes from the photodissociation of Hydrogen Halides : production, detection, and applications in Magnetometry

Alternative Title

Υπερύψηλες πυκνότητες πολωμένου κατά σπιν Υδρογόνου μέσω φωτοδιάσπασης Υδραλογόνων: παραγωγή, ανίχνευση και εφαρμογές στη Μαγνητομετρία

Author

Σπηλιώτης, Αλέξανδρος Κ

Thesis advisor

Ρακιτζής, Πέτρος

Abstract

Recently, our group has produced spin-polarized hydrogen (SPH) atoms at densities of at least 10¹⁹19 cm^-3, from the photodissociation of hydrogen halide molecules with circularly-polarized UV light, and measured via magnetization quantum beats with a pickup coil. These densities are about 7 orders of magnitude higher than those produced using conventional methods, and they open up new fields of application, such as ultrafast magnetometry, the production of polarized MeV and GeV particle beams, such as electron beams with intensities about 10⁴ higher than current sources, and the study of polarized nuclear fusion, for which the reaction cross sections of D-T and D^-3He reactions are expected to increase by 50% for fully polarized nuclear spins. One of the important questions on the production of SPH via photodissociation that remained open was the depolarization rate of the Hydrogen isotope fragments produced in the “high density” regime, i.e. at the limit where all Hydrogen halide molecules are photodissociated, and only SPH and halide radicals exist at the photodissociated volume. At this limit, spin-exchange collisions between SPH and Cl are expected to quickly depolarize SPH. However, work by Sofikitis et al demonstrated depolarization lifetimes of order ∼ 10 ns for SPH and SPD produced from the photodissociation of HBr and DI, respectively, much longer than expected if the hydrogen-halide spinexchange cross-section was comparable to the hydrogen-alkali value. Studies in HCl, in densities of an order of magnitude higher, were conducted, and the results are demonstrated in this study. The H-Cl spin-exchange cross-section is estimated to be σ_SE_H−Cl = 7×10^-17cm², which is the first measurement of this quantity. The high density of SPH produced with this method can also be utilized for the development of a sensitive, nanosecond-resolved magnetometer. The population transfer between the hyperfine states offers a fast, reliable modulation at one of the most well-known physical quantities in the world, the hyperfine frequency of Hydrogen f=1.420405 GHz. This modulation can be utilized to detect weak, time-dependent magnetic fields which induce a splitting in the hyperfine states of Hydrogen. In this study, a proof-of-principle of this novel instrument is demonstrated, with the detection of μT magnetic fields in a second, via direct measurements of the hyperfine beating frequencies. Furthermore, we demonstrate a detailed proposal for achieving nanosecond-resolved measurements, with sensitivites of order pT/pulse.

Language

English

Subject

Alignment

Photodissociation

Polarization

Spin-polarized particles

Πολωμένα άτομα

Πολωμένα μόρια

Πόλωση

Υδρογόνο

Issue date