The data listed below concern the forbidden triplet-singlet absorption bands of CO, originating from the X 1S+ (v=0) level and involving the a'3S+, e3S-, and d3Dstates.
The line positions and intensities of 41 of these bands are tabulated up to J=6 in the published version and up to J=33 here. These data were obtained using an improved model developed in a previous paper (Rostas et al., 2000, J. Chem. Phys., 112, 4591).
When possible, the calculated results are compared to experimental or observed ones, both for line positions and for oscillator strengths. The measured band oscillator strengths average to 94% of the calculated ones. A large majority of the measured values (27 out of 35) are within +/- 15% of the calculated ones. Thus, in view of the experimental uncertainties, it appears that the current calculated set of oscillator strengths can safely be used for the analysis of future absorption spectra involving the CO intercombination bands.
Absorption in the A1P(v)-X1S+(0) bands is commonly used to measure the column density of CO molecules in various astrophysical media especially in interstellar clouds (Morton and Noreau, 1994 and references therein). In the 1300 to 1600 Å range these bands have relatively large oscillator strengths and they tend to saturate when high column densities have to be measured. In such cases, the intersystem absorption bands, typically triplet-singlet bands, originating from the X1S+ (v=0) level and involving the a' 3S+, e3S-, and d3D states, can advantageously be used in view of their low oscillator strengths. These transitions are normally forbidden, but, due to the interaction of their upper state with the A 1P state, a small fraction of the A-X transition intensity is transferred to the intersystem transition. A few of these band oscillator strengths have been measured in the laboratory (Eidelsberg et al., 1992, Wu et al., 1999, Rostas et al., 2000, Stark et al., 2002) and/or in interstellar clouds (Federman et al., 1994, Jolly et al, 1998, Sheffer et al., 2002). These and some others, listed in Morton and Noreau (1994), have been calculated using mixing coefficients determined from the spectroscopic analysis of the A-X and intercombination transitions (Field et al., 1971, 1972a,b and Le Floch et al., 1987, 1989). The experimental and calculated results are not always in good agreement. Federman et al. (1994), in particular, have pointed out some large discrepancies between band intensities they measured in interstellar clouds and those listed by Morton and Noreau. In a previous paper (Rostas et al., 2000), referred below as Paper I, the present authors and colleagues have developed a model that resolves these contradictions. The major innovation of that model was that the forbidden bands were allowed to borrow intensity through simultaneous interaction with several vibrational levels of the A state whereas, in the standard model used in the calculations reported in Morton and Noreau (1994), only the nearest A(v) level was considered. When proper account is taken of the signs of these contributions, the improvement is striking and all the existing discrepancies are essentially suppressed. This model was further validated in the same paper by low resolution absorption cross-section measurements performed using synchrotron radiation from the LURE SUPER-ACO facility at Orsay. Recent high-resolution measurements performed by Stark et al. (2002) at Tsukuba are in general agreement with these results although a significant though much reduced discrepancy persists for one band, i.e. d 3D (v=7) - X1S+ (v=0). New interstellar measurements by Sheffer et al. (2002) are in generally good agreement with ours, especially for this band. The results tabulated in Paper I concerned the integrated oscillator strengths of 18 bands selected in view of possible comparisons with available experimental results. For practical applications in astrophysics and elsewhere a line-by-line listing is needed to calculate spectra that can subsequently be least squares fitted to the observed ones. For this purpose, the procedure developed in Paper I has now been applied to all the intersystem bands that have been recorded and spectroscopically analyzed by Herzberg and colleagues (1955, 1970). A few more have been included for comparison purposes. The tables included in the present paper version of this work have been limited to J''=6 in view of their use in the analysis of low temperature spectra obtained in interstellar clouds. Tables running up to J''=33 are available upon request.
The condensed notation defined in Paper I will generally be used herafter. Thus, intersystem transitions involving the X1S+ (v=0) ground state such as the above one (i.e. 3D (v=7) - X1S+(v=0))will be written as d7.
Extensive use has been made in this work of the tools developed with the co-authors of Paper I: Joëlle Rostas, Antoine Jolly, Jean-Louis Lemaire and André Le Floch. Initial discussions with Hélène Lefebvre-Brion and Robert W. Field have also provided a decisive contribution.
Eidelsberg, M., Rostas, F., Breton, J. & Thieblemont, B. 1992, J. Chem. Phys.,96, 5585
Eidelsberg, M., Jolly, A., Lemaire, J.L., Tchang-Brillet, W.-Ü L, Breton, J. & Rostas, F. 1999,
A&A, 346, 705
Federman, S.R., Cardelli, J. A., Sheffer, Y., Lambert, D. L. & Morton, D.C. 1994, ApJ., 432, L139
Field R.W. 1971, Thesis Harvard University
Field, R.W., Wicke, B.G., Simmons, J.D. & Tilford, S.G. 1972a, J. Molec. Spectrosc.,44, 383
Field, R.W., Tilford, S.G., Howard, R.A. & Simmons, J.D. 1972b, J. Molec. Spectrosc.,44, 347
Jolly, A., Lemaire, J.L., Belle-Oudry, D., Edwards, S., Malmasson, D., Vient, A. & Rostas, F. 1997,
J. Phys. B: At. Mol. Opt. Phys., 30, 4315
Jolly, A., McPhate, J.B., Lecavelier, A., Lagrange, A.M., Lemaire, J.L., Feldman, P.D., Vidal Madjar, A., Ferlet, R., Malmasson, D, Vient, A. & Rostas, F. 1998, A&A, 329, 1028
Herzberg, G., & Hugo, T.J. 1955, Canadian J. Phys., 33, 757
Herzberg, G., Hugo, T.J., Tilford, S.G. & Simmons, J.D. 1970, Canadian J. Phys., 48, 304
Lefebvre-Brion, H. & Field, R.W., 1986, Perturbations in the spectra of diatomic molecules, Academic Press , pp. 183 and following
Le Floch, A., Launay, F., Rostas, J., Field, R.W., Brown C. M. & Yoshino K., 1987 J. Molec. Spectr., 121, 337
Le Floch, A. 1989, Thesis, Université de Paris-Sud
Morton, D.C. & Noreau L. 1994, ApJS., 95, 301
Rostas, F., Eidelsberg, M., Jolly, A, Lemaire, J.L., Le Floch, A, & Rostas, J. 2000,
J. Chem. Phys., 112, 4591 (Paper I)
Simmons, J.D., Bass, A.M. & Tilford, S.G. 1969, ApJ 155, 345
Simmons, J.D. & Tilford, S.G 1971, J. Res. NBS, 75A, 455
Sheffer, Y, Federman, S. R., & Lambert, D.L. 2002, ApJL, in press
Stark, G., Smith, P. L., Yoshino, K., Esmond, J.R., Matsui, T., & Ito, K. 2002, ApJS, 138, 305
Wu, C.Y., Chen, F.Z., Judge, D.L., Hua Xin-Min, & Caldwell, J., J., 1999, Chem. Phys., 110, 267
Table 2. - Line by line listing of the a'3S+(v)-X1S+(0) bands.
Only those bands including lines of oscillator strengths above 10-6 are listed. The branch notation has been simplified in the tables: For example: PQ1 appears as the Q branch of the F1 sub-band. Similarly PP2 and RR2 appear as the P and R branches of the F2 component.
Table 3. - Line by line listing of the d3D(v)-X1S+(0) bands
Same comments as for Table 2. For example: PP2, QQ2 and RR2 appear as the P, Q and R branches of the F2 component.
Table 4. -Line by line listing of the e3D-(v)-X1S+(0) bands
Same comments as for Table 2. For example: QQ2 is the Q branch of the F2 sub-band. OP1 and QR1 are the P and R branches of the F1 sub-band.
Table5. - Comparison of the present calculated band integrated oscillator strengths with previously available results.
The earlier values are normalized to the present calculated ones.
MN=Morton & Noreau (1994); Fed.=Federman et al. (1994); Sheff.=Sheffer et al. (2002); Stark=Stark et al. (2002) Rost.= Experimental values of Paper I
* Value for d5 calculated at 15K
** d5 measured at 15K by Jolly et al. (1998)
*** d5 measured at 295K by Wu et al. (1999)
Figure 1. - Sub-band integrated oscillator strengths of the a'3S+(v)-X1S+(0) bands. Figure 2. - Sub-band integrated oscillator strengths of the d3D-X1S+(0) bands. Figure 3. - Sub-band integrated oscillator strengths of the e3S+-X1S+(0) bands. Figure 4. - Comparison of measured and calculated band integrated oscillator strengths.