Journal of the Vacuum Society of Japan

Selection of a Single Spin-rotational State of Molecular Oxygen by a Hexapole Magnet

Mitsunori Kurahashi, Yasushi Yamauchi

Published Jan 1, 2010• 0 citations

Abstract

O2 is one of the most important chemical species in every field of natural science. In the present study, a state-selected triplet molecular oxygen beam, in which nearly 100% of the molecules are in the spin-rotational state of (J, M)=(2, 2), has been produced by combining a supersonic seeded O2 beam with a hexapole magnet. The (2, −2) beam with >90% purity has also been obtained by a controlled non-adiabatic transition. The (2, ±2) beam, for which we can determine the spin and rotational angular momenta of O2 almost independently, is the most promising probe for studying the spin effects as well as the steric effects in O2 molecular scattering.

DOI: 10.3131/jvsj2.53.681

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Journal of the Vacuum Society of Japan

Selection of a Single Spin-rotational State of Molecular Oxygen by a Hexapole Magnet

Mitsunori Kurahashi, Yasushi Yamauchi

Published Jan 1, 2010• 0 citations

Publisher

Abstract

DOI: 10.3131/jvsj2.53.681

Related papers

Production of a single spin-rotational state [(J,M)=(2,2)] selected molecular oxygen (Σ3g−) beam by a hexapole magnet

Mitsunori Kurahashi, Yasushi Yamauchi

A state-selected O(2)((3)Sigma(g)(-)) molecular beam, in which nearly 100% of the molecules are in the spin-rotational state of (J,M) = (2,2), has been produced by combining a supersonic seeded O(2) beam with a hexapole magnet. The (2,-2) beam has also been obtained by the state inversion of the (2,2) beam through the nonadiabatic passage in a reversing longitudinal magnetic field along the beam axis. The intensities of the other (2,M) states, which appear when applying additional transverse magnetic fields to the reversing field region, were well reproduced by the Majorana's formula for J = 2. The (2,+/-2) beam, for which we can determine the spin and rotational angular momenta of O(2) almost independently, is the most promising probe for studying the spin effects as well as the steric effects in O(2) molecular scattering.A state-selected O(2)((3)Sigma(g)(-)) molecular beam, in which nearly 100% of the molecules are in the spin-rotational state of (J,M) = (2,2), has been produced by combining a supersonic seeded O(2) beam with a hexapole magnet. The (2,-2) beam has also been obtained by the state inversion of the (2,2) beam through the nonadiabatic passage in a reversing longitudinal magnetic field along the beam axis. The intensities of the other (2,M) states, which appear when applying additional transverse magnetic fields to the reversing field region, were well reproduced by the Majorana's formula for J = 2. The (2,+/-2) beam, for which we can determine the spin and rotational angular momenta of O(2) almost independently, is the most promising probe for studying the spin effects as well as the steric effects in O(2) molecular scattering.

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Collision cross sections and rate constants between two ground-state oxygen molecules are investigated theoretically at translational energies below $\ensuremath{\sim}1$ K and in zero magnetic field. We present calculations for elastic and spin-changing inelastic collision rates for different isotopic combinations of oxygen atoms as a prelude to understanding their collisional stability in ultracold magnetic traps. A numerical analysis has been made in the framework of a rigid-rotor model that accounts fully for the singlet, triplet, and quintet potential-energy surfaces in this system. The results offer insights into the effectiveness of evaporative cooling and the properties of molecular Bose-Einstein condensates, as well as estimates of collisional lifetimes in magnetic traps. Specifically, ${}^{17}{\mathrm{O}}_{2}$ looks like a good candidate for ultracold studies, while ${}^{16}{\mathrm{O}}_{2}$ is unlikely to survive evaporative cooling. Since ${}^{17}{\mathrm{O}}_{2}$ is representative of a wide class of molecules that are paramagnetic in their ground state we conclude that many molecules can be successfully magnetically trapped at ultralow temperatures.Collision cross sections and rate constants between two ground-state oxygen molecules are investigated theoretically at translational energies below $\ensuremath{\sim}1$ K and in zero magnetic field. We present calculations for elastic and spin-changing inelastic collision rates for different isotopic combinations of oxygen atoms as a prelude to understanding their collisional stability in ultracold magnetic traps. A numerical analysis has been made in the framework of a rigid-rotor model that accounts fully for the singlet, triplet, and quintet potential-energy surfaces in this system. The results offer insights into the effectiveness of evaporative cooling and the properties of molecular Bose-Einstein condensates, as well as estimates of collisional lifetimes in magnetic traps. Specifically, ${}^{17}{\mathrm{O}}_{2}$ looks like a good candidate for ultracold studies, while ${}^{16}{\mathrm{O}}_{2}$ is unlikely to survive evaporative cooling. Since ${}^{17}{\mathrm{O}}_{2}$ is representative of a wide class of molecules that are paramagnetic in their ground state we conclude that many molecules can be successfully magnetically trapped at ultralow temperatures.

arXiv:physics/0105085Physical Review AOct 2, 200166 citations

{\mathrm{O}}_{2}

molecules are particularly relevant for studies of inelastic and reactive processes.

We have demonstrated that supersonic beams of oxygen molecules

({\text{O}}_{2})

in the ground rotational state were slowed to a near standstill by a linear Zeeman decelerator and successfully confined spatially in an anti-Helmholtz magnetic trap. The translational temperature of the decelerated

{\text{O}}_{2}

molecules was about 800 mK. The demonstrated trapping capability of paramagnetic species opens up various possibilities for the investigation of cold collisions and reactions of various radicals in the sub-kelvin regime by spatially confining them in a magnetic trap.

{}^{17}{\mathrm{O}}_{2}

looks like a good candidate for ultracold studies, while

{}^{16}{\mathrm{O}}_{2}

is unlikely to survive evaporative cooling. Since

{}^{17}{\mathrm{O}}_{2}

is representative of a wide class of molecules that are paramagnetic in their ground state we conclude that many molecules can be successfully magnetically trapped at ultralow temperatures.