Using gnuplot to perform "visual fit"
# This script demonstrates user defined variables
# and user defined functions
a=7      # user defined
d=3      # user defined
f(x)=a*exp(-d*x*x)  # user defined
set xrange [-2:2]
set yrange  [0:a]
plot f(x)

having established this situation, you can now do the following:
gnuplot> a=5.5
gnuplot>  replot
gnuplot> d=4
gnuplot> a=5.2
And similar tests. If you also have some data, you can start by the
above definition, and then continue:
gnuplot> plot "data",f(x)
gnuplot> a=0.35
gnuplot> d=1.4
gnuplot> replot
until you have found a good combination of a,d which fits the data.
Task: consider this for the data in b2s1s etc. Which of the functions can be approximated by gaussian (in fact, most have simple exponential tail or 1/R, 1/R^2 behaviour....). Discuss this.