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A spectroscopic investigation of molecular ions occupying energy levels near dissociation

A spectroscopic investigation of molecular ions occupying energy levels near dissociation
A spectroscopic investigation of molecular ions occupying energy levels near dissociation

An ion beam technique, in which state selection is achieved by electric field dissociation, has been employed to measure microwave transitions of the D2+ and HeAr+ ions near their first dissociation limits. The design of the electric field dissociation lens has been examined in detail. The relatively simple three-plate lens created has been used to observe eight microwave transitions in D2+ which are components of the 2pσu - 1sσg electronic band system. Their measured frequencies are in excellent agreement with theoretical predictions. One transition involving the highest bound level of the 1sσg ground state shows an unexpected hyperfine splitting. This is interpreted in terms of g/u symmetry breaking caused by the Fermi contact interaction.

A sixty-eight line spectrum has been observed in HeAr+. All of the levels involved lie within 8 cm-1 the lowest dissociation limit, He (1S) + Ar+(2P3/2). The Zeeman splittings produced by a small axial magnetic field have been measured for nearly every line. From these measurements the value of the total angular momentum J and effective g-factor of each level have been determined allowing an energy level pattern, consisting of thirty seven energy levels and involving 66 of the transitions, to be constructed. An effective Hamiltonian analysis of this data in a Hund's case (c) basis is presented. It achieves an electronic and vibrational assignment of most of the energy levels; the assignments are approximate, however, because very strong rotational-electronic coupling undermines the Born-Oppenheimer approximation. An analysis using a coupled channels method in a case (e) representation is also discussed. It avoids using the Born-Oppenheimer approximation and reproduces the position of the energy levels far more accurately. (DX183772)

University of Southampton
Marr, Adrian John
Marr, Adrian John

Marr, Adrian John (1994) A spectroscopic investigation of molecular ions occupying energy levels near dissociation. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

An ion beam technique, in which state selection is achieved by electric field dissociation, has been employed to measure microwave transitions of the D2+ and HeAr+ ions near their first dissociation limits. The design of the electric field dissociation lens has been examined in detail. The relatively simple three-plate lens created has been used to observe eight microwave transitions in D2+ which are components of the 2pσu - 1sσg electronic band system. Their measured frequencies are in excellent agreement with theoretical predictions. One transition involving the highest bound level of the 1sσg ground state shows an unexpected hyperfine splitting. This is interpreted in terms of g/u symmetry breaking caused by the Fermi contact interaction.

A sixty-eight line spectrum has been observed in HeAr+. All of the levels involved lie within 8 cm-1 the lowest dissociation limit, He (1S) + Ar+(2P3/2). The Zeeman splittings produced by a small axial magnetic field have been measured for nearly every line. From these measurements the value of the total angular momentum J and effective g-factor of each level have been determined allowing an energy level pattern, consisting of thirty seven energy levels and involving 66 of the transitions, to be constructed. An effective Hamiltonian analysis of this data in a Hund's case (c) basis is presented. It achieves an electronic and vibrational assignment of most of the energy levels; the assignments are approximate, however, because very strong rotational-electronic coupling undermines the Born-Oppenheimer approximation. An analysis using a coupled channels method in a case (e) representation is also discussed. It avoids using the Born-Oppenheimer approximation and reproduces the position of the energy levels far more accurately. (DX183772)

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Published date: 1994

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Local EPrints ID: 458439
URI: http://eprints.soton.ac.uk/id/eprint/458439
PURE UUID: 4365c3be-edb0-43d7-bc61-5bfd09e1e570

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Date deposited: 04 Jul 2022 16:49
Last modified: 04 Jul 2022 16:49

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Author: Adrian John Marr

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