Command DIFCRS
The command DIFCRS allows you to compute from previously determined S-matrix elements the
- differential cross sections
- diagonal quadrupole and octupole alignment moments [A0(2) and A0(4)]
- off-diagonal alignment moment [A2(2)]
- m-dependent cross sections
- steric (oriented) cross sections.
The units
of the cross setions are square Angstroms. The moments are dimensionless. The definition of the moments A0(2) and
A0(4) is given in C. H. Greene and R. N. Zare, J. Chem. Phys. 78, 6741 (1983). The off-diagonal
alignment moment (A2(2)) is defined here.
difcrs,{jobname},j1,in1,j2,in2,ang1,ang2,dang,ienerg,jtotend,ipr,mflag,stflag,α,β
where
{jobnam} the jobname under which the S matrices have been
stored {jobname}n.smt. Here n denotes the value of
the parameter ienerg (see below). These S matrices must
have been previously generated using
JLPAR = 0 (this
generates S matrices for both parities)
JTOT1 = 1 (ensuring the determination of
S-matrices at every partial wave)
WRSMAT = .true. (ensuring
that the S-matrices are written to file {jobname}.smt).
The default value of {jobname} is the value you have set with
the command JOB, or, if no
value has been set, {jobname}=JOB
j1,in1 rotational quantum number and additional index for
the initial state
j2,in2 rotational quantum number and additional index for the
final state
ang1,ang2 initial and final angle (in degrees)
dang step size (in degrees) for scan through angles.
ienerg the cardinal value of the energy for which the differential
cross section is computed. i.e. if ienerg = 2, then the
second energy S matrices [{jobname}2.smt] are used
jtotend the maximum value of Jtot included in determining the
scattering amplitude. 
The value of jtotend can not be larger than the
variable JTOT2 used in the initial calculation
ipr
If ipr = 0 (the default) the degeneracy-averaged differential cross
sections and product rotational alignment and hexapole moments
are NOT printed to the normal output file
but only to the file {jobnam}n.dcs
if ipr .ne. 0, the differential cross sections and the alignment (A0(2)) and
hexapole moments (A0(4)) of the products are
also printed to the normal output file and to stdout.
mflag
If mflag = 0 (the default) only the degeneracy-averaged
differential cross section and the alignment (A0(2)) and
hexapole moments (A0(4)) of the products are calculated.
If mflag .ne. 0, then
- All m→m' differential cross
sections are calculated and printed. Quantization is in
the collision frame, where the initial relative
velocity vector defines the z axis.
- The integral m→
m' cross sections are
determined, by integration from ang1 to ang2 in steps
of dang.
- The diagonal (ρm,m) and the real part of the 2nd supra-diagonal
(ρm,m+2) elements of the rotational density matrix of the scattered products are
output into file {jobnam}n.rho.. These quantities are defined here in terms
of the scattering amplitudes.
stflag
stflag = 0 is the default. If stflag .ne. 0, then
"heads" and "tails" steric cross sections are calculated
(see M. H. Alexander, Faraday Discuss. 113, 437 (1999).
This is only allowed if flaghf = .true.
and basisty = 3
(doublet pi). If stflag .ne. 0, then the following
two parameters must be defined:<
α, β parameters which define the mixture of e and f
lamda-doublet states in the "heads" or "tails" orientation.
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