The
purpose of this program is to generate frequency and intensity data for
calibration of all types of rotational spectrometers ranging from the
cm-wave to the sub-mm wave regions. The program aims to predict
transitions for as many isotopic species and vibrational states as
possible. OCS is run from a graphical
control interface, which allows
- selection of the J range for the
calculation
- selection of the temperature
- selection of the intensity cutoff
- selection of all or of a required subset of
the thirteen available isotopic species
The
program produces output in the form of ASCII tables in the .ASR format and the
assumptions made in the calculation are clearly specified at the end of
each table. These tables can be displayed graphically and browsed
through with the program ASCP
by using the batch input
file provided below. Since ASCP can
display six quantum numbers for each energy level, and only J
is required for rotational labelling, the other quantum number fields
are used to indicate the three vibrational quanta (v1,
v2, v3), the value of l associated with v2,
and the isotopic masses of the oxygen, carbon, and sulfur atoms (as
visible in the snapshot below).
Predictions are based on the work of the Louvain group of Professor
Andre Fayt (Fayt@fyam.ucl.ac.be), to whom I am grateful for providing the most recent data.
The primary publications for the Louvain data as used by the program
are:
| 16O12C32S |
A.Fayt,
R.Vandenhaute, J.G.Lahaye, J.Mol.Spectrosc. 119,
233-266(1986)
Effective constants in J(J+1)
power series expansion for vibrational levels up to 4950 cm-1
|
| 16O12C34S,
16O13C32S, 18O12C32S |
J.G.Lahaye,
R.Vandenhaute, A.Fayt, J.Mol.Spectrosc. 123,
48-83(1987)
Effective constants in J(J+1)
power series expansion for vibrational levels up to 2500 cm-1
|
| 16O13C34S,
17O12C32S, 16O12C36S,
18O12C34S,16O13C33S,
18O13C32S, 17O12C34S,
18O12C33S |
L.S.Matsukidi,
J.G.Lahaye, A.Fayt, J.Mol.Spectrosc. 154,
137-162(1992)
Effective constants in J(J+1)
power series expansion for vibrational levels up to 4000 cm-1
|
| 16O12C32S |
J.G.Lahaye,
R.Vandenhaute, A.Fayt, J.Mol.Spectrosc. 119,
267-279(1986)
Effective dipole moments for states up to
4950 cm-1 - these are assumed to be isotopically invariant
by the program
|
| In addition: |
| 16O12C32S,
16O12C33S, 16O12C34S,
16O13C32S, 17O12C32S,
18O12C32S |
Most recent effective
constants for vibrational levels up to 5000 cm-1 in J(J+1)
power series expansion kindly provided by Professor Fayt and
redetermined in a refit of the updated primary data performed in March
2001.
For these six isotopic
species these constants have been used instead of the values published
in the earlier papers.
|
Current limitations:
- no hyperfine structure on the 33S
and 17O isotopologues
- unreliable frequencies for some of the most
strongly interacting states, such as (1,0,1) and (1,44,0)
for 16O12C32S, which are only 0.45 cm-1
apart and the perturbation is too strong for satisfactory description
with the effective power series description
- several limitations in the accuracy of the
calculation of the maximum absorption coefficient arising from the
assumptions concerning the dipole moments, the half width parameter,
and calculation of the population of the lower level.
|
