
==============================  xmlayer   =====================================

 Mlayer is a widget based graphical interface to calculate multilayer 
 reflectivities as a function of either the photon energy or incident angle.

 Limitations: This code only handles elements as materials (no mixtures or
 compounds implemented). It does not calculate the influence of interface 
 roughness.
.
 The mlayer code has been witten by J.H. Underwood at CXRO and is part of the 
 SHADOW package. M. Sanchez del Rio has modified it to directly call 
 an optical library, which gives correct values of refraction indeces when the 
 energy is scanned.  The XOPPY interface prepares a file containg using XRAYLIB\
 containg this information

 Schematic representation of the multilayer:

               vacuum
    |------------------------------|  \
    |          odd (1)             |  |
    |------------------------------|  | BILAYER # n_bilayers
    |          even (2)            |  |
    |------------------------------|  /
    |          .                   |
    |          .                   |
    |          .                   |
    |------------------------------|  \
    |          odd (2n - 1)        |  |
    |------------------------------|  | BILAYER # 1
    |          even (2n)           |  |
    |------------------------------|  /
    |                              |
    |///////// substrate //////////|
    |                              |


Description of mlayer input parameters:
=======================================



LAYER PERIODICITY: Multilayer may be periodic or aperiodic. In the first
  case you may define the number of layer pairs and the thickness of the
  two components of the pair. In the second case you must prepare a file
  containing two columns and N rows, one row for each pair.
  The first element of the column is the thickness in A of the odd element and
  the second column is the thickness of the even element.

SCANNING VARIABLE: Grazing angle [deg] or Photon Energy [eV]

MATERIAL PARAMETERS:
	Create on the fly: the material parameters are created by mlayer
                     and placed in a file mlayer.f12 (which overwrites previous
                     versions).
        Use existing file: mlayer.f12:  Do not create the mlayer.f12 file
                     and uses an existing one.
                     The mlayer.f12 file created "on the fly" can be edited by
                     hand customize the materials, optical constants,
                     densities, etc.

                     ****Note that the file mlayer.f12 is overwritten when the
                     "Material parameters" entry is set to "Create on the fly".

SUBSTRATE: Chemical symbol for the substrate.

ODD LAYER MATERIAL's chemical symbol for the odd layer

EVEN LAYER MATERIAL's chemical symbol for the even layer

PHOTON ENERGY: in eV

GRAZING ANGLE: in degrees

SCANNING VARIABLE STEP: the spep in either Photon energy or grazing angle,
  depending on your choice.

NUMBER OF SCANNING POINTS: obvious.

THICKNESS FOR THE ODD MATERIAL in A, when periodic Mlayers are considered.

THICKNESS FOR THE EVEN MATERIAL in A, when periodic Mlayers are considered.

NUMBER OF LAYER PAIRS when periodic Mlayers are considered.

FILE WITH LAYER THICKNESSES: file name with thicknesses as explained before,
  valid only when Individual layers are considered.



