Nanosecond control and high-density production of spin-polarized hydrogen atoms

Abstract

We demonstrate directly the nanosecond-timescale production of spin-polarized hydrogen (SPH) atoms from photodissociation of thermal HBr molecules, and the spin-state and Doppler-resolved detection using polarized fluorescence at 121.6 nm, without requiring hyperfine resolution. These techniques allow a variety of spin-dependent, nanosecond pump-probe experiments with SPH, which were not previously realizable. The potential of surpassing the SPH densities and production rates of current techniques is discussed.

( 2 + 1 ) laser-induced fluorescence of spin-polarized hydrogen atoms

“…However, we were able to take a qualitative scan of half of the Doppler profile, shown in Fig. 27,28 This maximum value is reduced by about 30% with respect to the result reported by Sofikitis et al 28 due to depolarizing collisions. The polarization of the H atoms is given by the intensity ratio ͓I͑R͒ −I͑L͔͒ / ͓I͑R͒ +I͑L͔͒, where R and L refers to right and left circular polarization of the probe laser, while the photolysis polarization was kept right circularly polarized.…”

“…27,28 A Polaroid-film linear polarizer was placed before the PMT, which allowed us to select between two different linear polarizations of the emitted photons.…”

“…Among the few examples are Cl and Br, [8][9][10][11] O, [12][13][14][15][16][17][18][19] S, [20][21][22][23][24][25][26] and, recently, H. 27,28 Most of these atoms can be prepared in an aligned or oriented distribution if particular photodissociation wavelengths and polarizations are chosen, as proposed by Van Brunt and Zare. 27,28 However, this method, using vacuum ultraviolet ͑VUV͒ radiation at 121.6 nm, involves technical complications related to the creation of the VUV radiation and the manipulation of its polarization under vacuum. 30 However, Rakitzis 31 proposed three polarization-sensitive fluorescence detection schemes that do not require hyperfine resolution.…”

Highly Nuclear-Spin-Polarized Deuterium Atoms from the UV Photodissociation of Deuterium Iodide

“…Polarized solid deuterium targets can be produced where the densities can reach as high as 2.5 × 10 19 spins/cm 3 , albeit in much lower polarization close to 10% [13]. Another approach for the production of polarized sold fuel involves accumulating the hyperpolarized deuterium in specially coated storage cells [11].Laser photodissociation of hydrogen halides has been shown to produce highly polarized H atoms [14][15][16][17]. The photodissociation process initially polarizes the electron spin up to 100% (for photofragment velocities parallel to the propagation direction of the circularly-polarized dissociation laser) [18]; due to the hyperfine interaction, the polarization oscillates back and forth between the electronic and the nuclear spin on the ∼1-ns timescale.…”

“…Laser photodissociation of hydrogen halides has been shown to produce highly polarized H atoms [14][15][16][17]. The photodissociation process initially polarizes the electron spin up to 100% (for photofragment velocities parallel to the propagation direction of the circularly-polarized dissociation laser) [18]; due to the hyperfine interaction, the polarization oscillates back and forth between the electronic and the nuclear spin on the ∼1-ns timescale.…”