Purpose: Enables plotting of time-dependent field.
 Usage:   showfield [-i -p -o -ti T0 -tf T -si S1 -sf S2 -ver -h -?]

Options : 
 -i DIR  : data is stored in directory DIR
 -o FILE : The ouput is written to file FILE.pl rather than to ./field.pl

 -ti T0 : Initial time is T0 (fs)
 -tf T  : Final time is T (fs)
 -si S1 : Initial State is S1
 -sf S2 : Final State is S1
 -op H: Evaluate operator H rather than system
 -ver    : Version information about the program.
 -h      : Print this help text. 
 -?      : Print this help text. 

  The program is menu driven. Just type "showfield" and then follow the menu. 
  By default the field will be plotted from -100 to 200 fs
  Use the options to choose the correct states and time.
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