Purpose: Computation of the spectrum by fourier-transforming
         the autocorrelation function.
         Three spectra are generated acording to the weight functions
         cos^n(pi*t/(2*T)) (n=0,1,2). The option -lin allows to use
         a second set of filters. In plspec the filters of this
         second set are enabled through the option -g3, -g4, or -g5.
         Additionally there is the weight function exp(-(t/tau)^iexp).
         The conversion factor from damping time to FWHM energy width
         is 1.32 eV fs and 2.2 eV fs for iexp=1 or 2, respectively.
         Input a zero for tau if not damping is required.

Usage : autospec [-f -i -o -e -n -r -ctr -ph -p -q -g -t -FT -EP -Mb -ver -h -? -inter] 
                   [emin emax unit tau iexp]

Options : 
 -f FILE : The autocorrelation is read from file FILE rather than from ./auto
           The string FILE may be a relative or full path-name.
 -i DIR  : Take DIR as input directory.
 -o FILE : The spectrum is written to file FILE.pl
           rather than to ./spectrum.pl
           The string FILE may be a relative or full path-name.
 -e R Unit : The offset energy is set to R in units Unit; e.g. 0.3 ev
             Note, a positive R shifts the spectrum to the right.
 -n      : The maxima of the three spectra are normalised to 1.
 -r      : Plot the resolution rather than the spectrum
 -ph  ph : Use phase correction exp(i*ph*1.0e-6_dop*t^2)
 -p I    : The no. of plot-points is I rather than 1000
           Use "-p 2000" for final plots
 -q I    : Same as -p.
 -lin    : A second set of filter functions is used, namely
           g(t) = cos^3(pi*t/(2*T) (column 2),
           g(t) = 1 - t/T (column 3),
           g(t) = (1-t/T)*cos(pi*t/T) + sin(pi*t/T)/pi (column 4).
           The last two filters yield a positive semi-definite
           Fourier-transform. When using plspec, these three filters
are chosen by the option -g3, -g4, or -g5, respectively.
           When the option -lin is not set, the columns 2,3, and 4
           refer to the filters cos^0, cos^1, and cos^2, respectively.

 -g ncos : GNUplot command lines are written to the output file.
           ncos is the exponent of the cosine damping function.
 -t tcut : The autocorrelation function is read only up to t=tcut
 -FT     : No multiplication with the energy prefactor. Fourier
           transform only. (default!)
 -EP     : Multiplication with the energy prefactor.
 -Mb norm: Absorption spectrum in Mb. norm is ||D*Psi|| (in au)
           where D is the Dipole moment. -Mb sets -EP.
 -ctr    : Perform a sin-transform rather than an exp one.
           (This is for ctrace files.)
 -nofs   : No transformation to fs. Use when 'time-not-fs' was set in mctdh.
 -ver    : Version information about the program 
 -inter  : Interactive plotting 
 -h      : Print this help text. 
 -?      : Print this help text. 
Following the options one may provide the arguments (separated by blank):
           Emin, Emax, Unit, tau, iexp 
If not enough arguments are given, the user is prompted for the missing 
arguments. Use the Unit 'no' if the propagation is run with the
keywords: 'time-not-fs','energy-not-ev'.
When using the options -EP or -Mb one must make sure that the zero point
of the energy is set appropriately. Use the option -e if the total energy
differs from photon energy. 1 Mb = 10^-18 cm^2. The norm ||D*Psi|| can be
found in the log file of the operate run.
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