HREELS data handling and simulation

Set of data analysis routines for surface vibrational spectroscopy based on a Delta05 spectrometer with software from VSI or SPECS.

Simple data reading and plotting routines are provided, but also advanced routines for in depth analysis. A fast data browser as graphical user interface is included as ViewHREELS.py. It can also take command line arguments.

Additional a python interface to a Fortran-based calculation of full HREEL spectra is provided in class lambin (in calcHREELS20.py). Note that this part requires a local compilation (via "f2py3 -c -m myEels20 myEels20.f90") from the Fortran90 files. Only for the Linux-based python version 3.8, there are complied files provided. For details see below.

Most of the routines are within the class HREELS (HREELS.py). A simple command line program is "showHREELS.py", which reads one data file and plots the spectrum with a second amplified trace.

Usage:  >python showHREELS.py filename [factor wavenumber]

    E.g.: python showHREELS.py H9H03 100 53 

More general usage:

Read dataset by calling the HREELS class: data1 = HREELS('filename', datapath='datapath') # Here you can omit the extension '.gph' # The second argument is optional

This will assign/calculate the following properties:

data1.filename
data1.datapath
data1.startTime
data1.stopTime
data1.totalTime
data1.timePerChannel
data1.numberOfSegments
data1.energy    # Electron kinetic energy
data1.filament  # Filament current in Ampere
data1.segments  # list of segment info
data1.data      # [(-100.1021616, 259.5), (-98.5374352, 264.5), ...]
data1.xdata
data1.ydata
data1.maxIntensity  # Count rate of elastic peak
data1.resolution    # width of elastic peak

The following methods are defined within the class:

info()      :   Print information about the spectrum
plot()      :   Draws the spectrum. Optional arguments are:
                (xmin=None, xmax=None, factor=1, label='x', normalized=False, color="b-",marker=True)

plotInfoAmp()   Draws spectrum together with amplified trace.
pickPeak()  :   Select peak by mouse cursor. The call of figure() is required before.
selectData():   Returns the data between wavenumbers x1 and x2
findIndex(lossenergy): Returns the data array index for a given energy loss
setMarker(x, y, ymin=0, size=None): Sets vertical marker with text label 
plotWaterFall(...):

calcHREELS20

These routines are based on the publication "Computation of the surface electron-energy-loss spectrum in specular geometry for an arbitrary plane-stratified medium" by P. Lambin, J.-P. Vigneron, and A. A. Lucas, in the Journal "Computer Physics Communications 60, 351-64(1990)".

The code is modified to comply with Fortran90 and wraped to python functions. See the example in Examples/calcHREELS1.py for NiO(001). The parameters for epsilon_infinity "eps": 5.25, as well as frequency and width for the TO phonon, "wTO": [393.7], "gTO": [10.8], and the LO phonon, "wLO": [584.7], "gLO": [10.8], need to be specified.

Complex calculations for perovskite oxides are provided in the examples calcHREELS2.py and calcHREELS3.py.