Photoexcitation of anthracene generates the spin triplet $)=(1$ excited state. The X$-$band EPR $(9\mathrm{.}50GHz)$ spectrum from a frozen solution at $77K$ is shown below.

The spectrum can be downloaded for analysis as a text file $($q$4\_$anthracene$\_$triplet.txt$)$ containing field:intensity data that can be plotted in any standard software.

$($i$)$ With the aid of a suitable energy level diagram, explain how many fully$-$allowed EPR transitions should be observed for each orientation of the molecule with respect to the applied magnetic field.

$[2$ marks$]$

$($ii$)$ Identify the $z$ transitions from the spectrum, and give the separation between them in magnetic field units $(mT)$ and in $MHz($assume $g=g_e).$

$[2$ marks$]$

$($iii$)$ Identify the $x$ transitions from the spectrum, and give the separation between them in magnetic field units $(mT)$ and in $MHz($assume $g=g_e).$

$[2$ marks$]$

$($iv$)$ Identify the $y$ transitions from the spectrum, and give the separation between them in magnetic field units $(mT)$ and in $MHz($assume $g=g_e).$

$[2$ marks$]$

$($v$)$ Determine the axial $(|D|)$ and rhombic $(|E|)$ zero$-$field splitting parameters for the triplet state $($MHz units$).$

$[2$ marks$]$

$($vi$)$ Determine the rhombicity parameter $(\frac{E}{D})$ for the triplet state.

$[1$ mark$]$

$($vii$)$ A similar experiment on benzene gives $|D|=4\mathrm{.}7GHz$ and $|E|=600MHz.$ Explain the difference in the magnitude of $|D|$ between anthracene and benzene.

$[2$ marks$]$