Re: p- and s-polarization question

In sci.chem.analytical tzavalas <[EMAIL PROTECTED]> wrote:
: Since I am convinced that p-polarized light refers to an angle of 0 or
: 90 degrees I can't get how one can use "p-polarized light" at various
: angles.

Dear Spiros, 

Terms s- and p-polarized light are used when the light beam hits the 
surface. As you had figured out, in s-polarized and p-polarized and you 
have 90 degrees angle between their linear polarization. However, if you 
do not have a surface, there are many, many different ways to select two 
polarizations so that they have 90 degrees difference (for example 10 and 
100 or 25 and 115 degrees compared to some reference). When you have 
surface, two planes are defined in the system. First, you have the plane 
of the surface, for example Langmuir-Blodgett film. Second, when the beam 
hits the surface, at least part of it is reflected (and refracted), so we 
have on our surface the beam contact point, and two lines leaving from 
that contact point: the incoming beam and the reflected beam. 
They define the other plane in the system, the plane of incidence. 
p-polarized light has linear polarization along the plane of incidence, 
s-polarized light has linear polarization at 90 degrees angle to the plane 
of incidence. I searched google with s-polarized and angle of incidence 
and found the following page, which has a figure which probably clarifies 
my explanation: 
http://www.uta.edu/optics/research/ellipsometry/ellipsometry.htm

Of course it is possible to have different angles between the light beam 
and the surface. Accordingly, if you have molecules with their transition 
dipole moments oriented somehow in the surface (for example in the LB 
films), then when you change the angle at which the light beam hits the 
surface, you also change the angle between the linear polarization of 
p-polarized light and the surface (LB film) normal. Thus if the absorption 
dipole moments of the molecules are oriented in the film, the relative 
absoption of s- and p-polarized light will change with the angle of 
incidence (consider square of dot product of (absorption) transition 
dipole moment vector and the light polarization vectors).

I hope this helped.

    Best regards,
                      Juha-Matti Alakoskela


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