arXiv subjects

C. S. Kannis

Publications and source records attributed to C. S. Kannis.

6 recordsLinked to original sources

arXiv2026

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

We propose schemes to produce highly nuclear-spin polarized small molecules in an intense and cold molecular beam via microwave or infrared rotational excitation, followed by hyperfine-induced quantum beats. Repumping schemes can be used to achieve polarization above $90\%$ in cases where single-pumping schemes are insufficient. We discuss the possibility of high production rates which allow applications including nuclear-magnetic-resonance signal enhancement, and spin-polarized nuclear fusion, where polarized nuclei are known to enhance D-T and D-$^3$He fusion cross sections by $50\%$.

physics.chem-ph↗

arXiv2023

A Universal Method to Generate Hyperpolarisation in Beams and Samples

Sizable hyperpolarisation, i.e. an imbalance of the occupation numbers of nuclear spins in a sample deviating from thermal equilibrium, is needed in various fields of science. For example, hyperpolarised tracers are utilised in magnetic resonance imaging in medicine (MRI) and polarised beams and targets are employed in nuclear physics to study the spin dependence of nuclear forces. Here we show that the quantum interference of transitions induced by radio-wave pumping with longitudinal and radial pulses are able to produce large polarisations at small magnetic fields. This method is easier than established methods, theoretically understood and experimentally proven for beams of metastable hydrogen atoms in the keV energy range. It should also work for a variety of samples at rest. Thus, this technique opens the door for a new generation of polarised tracers, possibly low-field MRI with better spatial resolution or the production of polarised fuel to increase the efficiency of fusion reactors by manipulating the involved cross sections.

physics.atom-ph↗

arXiv2021

Macroscopic production of highly nuclear-spin-polarized molecules from IR-excitation and photodissociation of molecular beams

Pure, highly nuclear-spin-polarized molecules have only been produced with molecular beam-separation methods, with production rates up to ${\sim}3{\times}10^{12}$ s$^{-1}$. Here, we propose the production of spin-polarized molecular photofragments from the IR-excitation and photodissociation of molecular beams, with production rates approaching the tabletop-IR-laser photon fluxes of $10^{21}$ s$^{-1}$. We give details on the production of spin-polarized molecular hydrogen and water isotopes, from formaldehyde and formic acid beams, respectively. Macroscopic quantities of these molecules are important for NMR signal enhancement, and for the needs of a nuclear fusion reactor, to increase the D-T or D-$^{3}$He unpolarized nuclear fusion cross section by ${\sim}50{\%}$.

physics.chem-ph↗

arXiv2021

Macroscopic production of spin-polarized hydrogen atoms from the IR-excitation and photodissociation of molecular beams

We describe methods for the production of spin-polarized H and D atoms from the IR-excitation and photodissociation of molecular beams of HBr, HI, and ${\rm NH_{3}}$ isotopes, including optical excitation schemes with partial hyperfine resolution. We discuss the extent to which the production rates may approach the IR-laser production rates of ${\rm 10^{21}\, photons\, s^{-1}}$, and how the production rates of conventional methods of ${\sim}{\rm 10^{17} \, s^{-1}}$ may be surpassed significantly.

physics.atom-ph↗

arXiv2020

Exploiting the Planck-Einstein Relation

The origin of quantum physics was the discovery of the base unit of electromagnetic action $h$ by Max Planck in 1900 when he analyzed the experimental results of the black body radiation. This permitted Albert Einstein a few years later to explain the photoelectric effect by the absorption of photons with an energy of $E = h \cdot f$. We exploit the Planck-Einstein relation in a new type of fundamental spectroscopic measurements of direct transitions between two states with energy differences of about 10 neV and induced frequencies of a few MHz. Employing a Lamb-shift polarimeter and a Sona transition unit, featuring a relatively simple magnetic field configuration of two opposing solenoidal coils, we were able to determine $f$ and measure $E$ independently. Only resonances corresponding to integer multiples of Planck's constant $h$ were observed in our setup, which can very well be explained quantitatively by the Schrödinger equation. This new method beautifully demonstrates the quantization in the micro-cosmos and allows one to measure the hyperfine splitting energies between the substates with $F=1$ and $m_F = -1, 0, +1$ of metastable hydrogen atoms as function of a magnetic field and, thus, to investigate the influence of QED corrections on the Breit-Rabi diagram.

physics.atom-ph↗

arXiv2020

Production of HD Molecules in Definite Hyperfine Substates

Polarized atomic beam sources have been in operation since many years to produce either nuclear polarized atomic hydrogen or deuterium beams. In recent experiments such a source was used to polarize both isotopes independently at the same time. By recombination of the atoms, HD molecules with all possible nuclear spin combinations can be created. Those spin isomers are useful for further applications like precision spectroscopy, as polarized targets for laser-particle acceleration, polarized fuel for fusion reactors or as an option for future measurements of electric dipole moments.

physics.atom-ph↗