About OpAbsorption and Rayleigh Process in OpNovice2 example

Dear experts,
I am trying to understand the Rayleigh attenuation length and ABSLENGTH value in the OpNovice2.mac and wls.mac. There are some points confusing me:

1.What is the unit used in ABSLENGTH ? Is it mm , cm or m ?
e.g /opnovice2/boxProperty ABSLENGTH 0.000002 1 0.000005 2 0.000008 3

2.Is the Rayleigh Attenuation Length index necessary in the simulation? If I want to define a kind of material but no RAYLEIGH value, How to use Rayleigh scattering process in this G4OpticalPhysics ?
e.g /opnovice2/boxProperty RAYLEIGH 0.000002 1 0.000008 1

Any help from yours would be sincerely appreciated .

Looking forward to your reply.


Hmm, the README says “values are in Geant4 internal units” which maybe isn’t helpful. Distances are in mm.

If no value for Rayleigh is specified, there is no Rayleigh scattering. Conversely, in this or any application using G4OpticalPhysics constructor, if there are values specified for an optical process, and the process isn’t manually turned off, the process will occur.

The idea of OpNovice2 is to make it easy to experiment to see what happens…

Thanks for your answer sincerely!
That helps a lot!
Actually There is another question about G4OpAbsorption process.
The explanation for the process in book is this:

I am wondering if I input the nonlinear absorption length value to ABSLENGTH, does the G4OpAbsorption process have ability to represent the photon nonlinear absorption partly?

The histogram of number of particles vs. distance travelled is given by
f(x) = 1 - exp(-x/ABSLENGTH)

Is that what you mean by nonlinear?

Ammm I think not…
Nonlinear absorption I wanted to say includes such as two-photon absorption and multiphoton absorption physical processes.
But the formula may say the G4OpAbsorption process may only stand for the linear process…
My many questions have been solved. Thanks for your reply!

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