From the post "Beijing Mask Opera and Wobbling Hydrogen",
Ft=mea=q24πεor2cos(θ) --- (1)
When v=c,
r=q24πεomec2sin2(θ)=xcos(θ) --- (2)
x=q24πεomec2sin2(θ)cos(θ)
dxdθ=−q24πεomec2(2cos2(θ)sin(θ)−sin3(θ))
The negative sign is the result of x decreasing as θ increases.
d2xdθ2=−q24πεomec2(2cos3(θ)−7cos(θ)sin2(θ))
d2xdθ2dθ2d2t=dx2dt2=−q24πεomec2(2cos3(θ)−7cos(θ)sin2(θ))dθ2d2t --- (*)
Substitute (2) into (1)
mea=4πεom2ec4q2cos(θ)sin4(θ)
a=4πεomec4q2cos(θ)sin4(θ)=dx2dt2
From (*),
4πεomec4q2cos(θ)sin4(θ)=−q24πεomec2(2cos3(θ)−7cos(x)sin2(θ))dθ2d2t
16π2ε2om2ec6q4=−sin4(θ)(2cos2(θ)−7sin2(θ))dθ2d2t
16π2ε2om2ec6q4∬T0d2t=−∬π20.9553sin4(θ)(2cos2(θ)−7sin2(θ))dθ2
This was solved on the web,
−∫π20.955∫sin4(θ)(2cos2(θ)−7sin2(θ))dθdθ=2358870+31280000−33π2128+103cos(191100)128−23cos(19150)256+cos(573100)128
8π2ε2om2ec6q4T2=0.8927
And the period of this oscillation is 4T,
T=√0.8927q48π2ε2om2ec6
T=√0.89278q2πεomec3
Tp=4∗T = 4*( 0.8927/8)^(1/2)*(1.602176565e-19)^2/(pi*(8.854187817e-12)*(9.10938291e-31)*(299792458)^3)
Tp = 5.02388e-23 s
And the resonance frequency is,
f = 1.9905e22 Hz
Comparing this to the previous estimate, this value is fair. It is expected that the oscillation frequency be higher because the system is not linear (1r2) as was the first estimate. The correction factor is pi/4*(8/0.8927)^(1/2) = 2.3511.