| Summary: | A laser ablation source has been constructed for a pulsed jet cavity Fourier transform
microwave (FTMW) spectrometer. This source is mounted in one of the microwave
cavity mirrors and includes a mechanism for rotating and translating the target metal
rod. Seven metal-containing species, namely MgS, MgBr, AlBr, MgNC, A1NC, Y F and
YBr, have been prepared using this apparatus and their pure rotational spectra have
been measured by FTMW spectroscopy.
The first laser ablation-FTMW measurement of a metal sulfide, MgS, has been made.
The J = 1 — 0 transition near 16 GHz has been measured for 4 isotopomers in the ground
vibrational state, as well as for the main isotopomer in the first excited vibrational state.
²⁵Mg nuclear hyperfine structure has been observed and the nuclear quadrupole coupling
constant has been determined.
The pure rotational spectra of magnesium monobromide and aluminium monobromide
have been measured between 9.3 and 20.1 GHz. For MgBr, this is the first report
of such a spectrum. Rotational, fine structure and several Br hyperfine parameters have
been obtained for this radical and an accurate equilibrium bond length has been determined.
From the nuclear quadrupole and magnetic hyperfine constants MgBr has been
found to be highly ionic, with the unpaired electron residing almost entirely on Mg.
For AlBr, accurate hyperfine parameters have been obtained, including the first values
for the Al⁸¹ Br isotopomer. These, too, are consistent with highly ionic bonding. The
calculated ionic characters follow trends predicted from electronegativity values: MgBr exhibits more covalent character than Ca and heavier alkaline earth monobromide species
and AlBr shows less covalent character than GaBr.
Pure rotational spectra of aluminium isocyanide and magnesium isocyanide have been
measured in the frequency range 11.9 - 23.9 GHz. The hyperfine structure in MgNC
caused by the 1 4 N nucleus has been measured and the nuclear quadrupole coupling, Fermi
contact and dipole-dipole interaction constants have been obtained. From the measured
transitions of A1NC, nuclear quadrupole coupling constants and nuclear spin-rotation
constants have been determined for both the ¹⁴N and the ²⁷A1 nuclei along with an Al-N
nuclear spin-spin constant. The degree of sp-hybridisation of the bonding orbitals of
A1NC and MgNC have been estimated from the nuclear quadrupole coupling constants.
Comparisons have been made to similar linear metal isocyanide and metal monohalide
species.
The first high resolution spectrum of yttrium monobromide has been measured between
7.4 and 22.5 GHz. In addition, nuclear spin-rotation splitting has been observed
in the spectrum of yttrium monofluoride. Equilibrium rotational parameters have been
determined for YBr and used to calculate an equilibrium bond distance. Hyperfine structure
due to the bromine nuclei has been observed and nuclear quadrupole and nuclear
spin-rotation constants have been determined. From them, YBr has been found to be
highly ionic and very similar in behaviour to the alkali metal bromide species. The
FTMW results for Y F have been combined with data from other pure rotational studies
to determine the nuclear spin rotation constant. === Science, Faculty of === Chemistry, Department of === Graduate
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