The M1/E2 mixing ratio δ = sqr(TE2/TM1),
where the T is the transition probability [1/sec].
In history, the sign convention of the mixing ratio is NOT consistent.
Here I only use + sign.
TE2 = (1/sec).
TM1 = (1/sec).
arctan(δ) = (deg.)
δ =
The numerical expressions for the E2 and M1 single-particle Weisskopf estimates:
( only a rough estimation.)
A = (atomic mass)
Eγ = (in the unit of MeV)
TE2 = (1/sec).
TM1 = (1/sec).
-----------------------------------
TE1 = (1/sec).
TM2 = (1/sec).
Formulae:
$\textrm{TE2}$ = $7.2 \times 10^{7} \,\, (E_{\gamma})^5 A^{4/3}$
$\textrm{TM1}$ = $5.6 \times 10^{13} (E_{\gamma})^3$
$\textrm{TE1}$ = $1.0 \times 10^{14} (E_{\gamma})^3 A^{2/3}$
$\textrm{TM2}$ = $2.2 \times 10^{7} \,\, (E_{\gamma})^5 A^{2/3}$
Note: M2 transitions are generally inhibited compared to the Weisskopf estimate by a factor at least 10, according to D. Kurath and R.D. Lawson, Phys, ReV. 161, 915.
Useful resources: slides from 2013 postgraduate summer school.