JONATHAN SILVERLIGHT asked ALISTAIR:
"How many dark energy particles are there per m^3"

ALISTAIR replies:

If the cosmic microwave background is losing energy because dark
energy is gradually absorbing microwave photons, the answer goes as
follows,assuming the universe has a small net magnetic field,and dark
energy particles have spin and charge and mass and can be promoted
from one spin energy state to another
by cmbr photons.
The average cmbr photon energy is about 10^-22 Joules.
So the difference in energy between dark energy particle spin states
in the magnetic field of the universe needs to be 10^ - 22 Joules.
An electron has a spin energy difference in a magnetic field of 10^ -
24 J/Tesla.
Looking at the equation for the magnetic moment of an electron:

u1 -u2 = (1/2 + 1/2) x g e h / 2 m = 10^ - 24

If we leave everything the same for dark energy particles but change
the mass
to 10^ -2 x mass of electron = 10^ -33 kg
then u1 -u2 for the dark energy particle = 10^ - 22 = energy of cmbr
photon

This is for a field of 1 Tesla.
The magnetic field of the universe as a whole is about 10^ -14 Tesla.

So u1 - u2 for the dark energy particle OF mass 10^ - 33 kg is
10^ - 22 x 10^ -14 = 10 ^ -36 J.

Therefore to absorb a cmbr photon with energy 10^ - 22 J the dark
energy particle must have a mass 10^ - 22/ 10^ - 36 times smaller = 10
^ 14 times smaller.This would be 10 ^ - 47 kg.

Since the density of dark energy particles is 10^ - 27 kg / m^3 then
there would be 10^ - 27 / 10 ^ -47 particles / m^3.
This is 10^ 20 particles/ m ^ 3

About 1000 dark energy particles for every millimetre in distance.