I can't get the paper from that page, the links there give 404 page not found.

This is because researchgate has only recognised half the link (and underlined it). When I copied the whole link it worked but went to a page where I would have to pay to see the paper.

kx=ωc(ϵ1ϵ2/ϵ1+ϵ2)^1/2 is unlikely to be correct because it is the same as kx=ωc(2ϵ2)^1/2, unless ϵ1ϵ2 is not the same as ϵ1 x ϵ2

k is usually proportional to ω, the proportionality is usually 1/v, where v is some kind of velocity. Often v=c/(ϵr)^1/2. Without more idea of the original I can't do more.

Should ωc be ω/c?

I suggest you read https://en.wikipedia.org/wiki/Surface_plasmon_polariton, where the equations look like I would expect them to.

hello!

I apologize for this : it is a book surface plasmons on smooth, rough surfaces by Raether

yes, it is w/c

Malcolm White : Hi, I did check, it is just the same thing, but I don't know if the real and the imaginary parts are obtained mathematically or assumed with the respective equations.

I was trying to substitute the dielectric permittivity to obtain the wave number equation, also I was trying to figure if there was a specific reason to assume |ε1′| >> ε1″, or it is just generally considered.

Thank you for your time and consideration

regards

Ketan

It just generally is. If you look up wikipedia you will see the equations and some values for |ε1′| and ε1″ Actually >> is not always true, so the approximate formulae are not very accurate in those cases.

You should be able to work them out for yourself. It is very simple matematics. Look at the formulae in the wikipedia article.