OCS calibration data for rotational spectroscopy

        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.

OCS.EXE The executable of the program, which has been written in the Delphi language by Oleksandr Desyatnyk of our group. It should run in any Win32 windows and you need to download both the executable and the ASCII data files given below
161232.res 161233.res 161234.res 161332.res 171232.res 181232.res 161236.res 161333.res 161334.res 171234.res 181233.res 181234.res 181332.res


The ASCII data files used by the program - the thirteen .RES files contain the effective constants in the J(J+1) power series expansion, and the OCS.DIP file contains the dipole moments for the 16O12C32S isotopologue, which are also used without change for all other isotopologues.

OCS.zip An alternative download in the form of a zipped archive containing all files necessary for running OCS.  Unpack into a directory of your choice and go.

OCS.INP The batch input file for reading into ASCP_L or ASCP of the data files written by OCS
OCS_SNAP.GIF Snapshot of the ASCP screen, displaying the region to high frequency from the J=30<-29 g.s. transition of the parent isotopologue, calculated for 298K.

Compare this with the annotated mm-wave RAD spectrum of OCS in Fig.1 of A.V.Burenin et al. J.Mol.Spectrosc. 85, 1-7(1981).

The ASCP cursor is positioned on the J=31<-30 rotational transition of 16O12C34S in the (1,0,0) vibrational state at lower level energy of 1031.2 cm-1, with transition frequency of 366588.43 MHz and with absorption coefficient of 5x10-5 cm-1. This information is displayed in the top two information lines. Parent isotopologue is in yellow, other isotopes are each in a different colour.


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