- Email: [email protected]
Line parameters for the A2Σ+−X2Π bands of OH
Journal of Quantitative Spectroscopy & Radiative Transfer 68 (2001) 225}230
Note
Line parameters for the A&>!X% bands of OH James R. Gillis , Aaron Goldman *, Glenn Stark, Curtis P. Rinsland Boeing Space & Communication Group, P.O. Box 3999 MS 8H-05, Seattle, WA 98124-2499, USA Department of Physics and Astronomy, University of Denver, 2112 E Wesley Avenue, Denver, CO 80208, USA Department of Physics, Wellesley College, Wellesley, MA 02481, USA Atmospheric Science Division, NASA Langley Research Center, Hampton, VA 23681-2199, USA Received 6 December 1999
Abstract Updated line parameters, including line positions and intensities, have been generated for the six strongest A&>(v )!X% (v ) bands of OH, i.e., v !v "0,#1, v "0, 1, 2, applicable to atmospheric and high G temperatures. Results from recent laboratory measurements and theoretical studies have been incorporated into the calculations. Tables of line parameters are available for 296 and 4600 K. 2000 Elsevier Science Ltd. All rights reserved.
The OH line parameters for the A&>(v "0)!X% (v "0) band generated almost 20 years G ago by Goldman and Gillis [1] have been used routinely in atmospheric and astrophysical studies (e.g., [2}12] and references therein). Other atmospheric UV studies of OH have used very similar values, e.g., Burnett and Burnett [13], Armerding et al. [14], Notholt et al. [15] and references therein. While UV}VIS line parameters are now a formal part of the HITRAN database [16], these OH lines have not been included yet in the database. The IR OH line parameters have been updated extensively in the recent work of Goldman et al. [17]. The calculations by Goldman and Gillis [1] were based on the spectroscopic constants of Destombes et al. [18] for energy levels and line positions, the relative Einstein coe$cients A(v J !v J ) of Chidsey and Crosley [19], and on the intensity normalization according to the rotationless (N "0) v "0 lifetime as measured by German [20], q "(0.688$0.007);10\ s. The line positions were estimated to be accurate to better than 0.1 cm\. In subsequent, unpublished, calculations, Gillis and Goldman [21] revised the A&>(v "0)!X%(v "0) line parameters calculations, using the spectroscopic constants of Coxon [22], with the previous [1] intensity normalization. The accuracy of the new line positions * Corresponding author. Tel.: #1-303-871-2238; fax: #1-303-871-4405. 0022-4073/00/$ - see front matter 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 2 - 4 0 7 3 ( 0 0 ) 0 0 0 1 1 - X
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was estimated to be better than 0.01 cm\. The line parameters for the A&>(v )!X%(v ), (v , v )"(1,1), (2,2), (1,0), (2,1), (3,2), were also calculated in that work. According to the recent work of Cageao et al. [8], the Goldman and Gillis (0,0) line parameters remain the adopted database. It was recognized, however, by Cageao et al. [8] that a signi"cant improvement in the (0,0), (1,1), (2,2) line positions was provided by the high-resolution FTS work of Stark et al. [23], but that no signi"cant change in the intensity normalization can be concluded from the available publications. Comparing (0,0), (1,1) and (2,2) line positions of Gillis and Goldman [21] with those lines from Stark et al. [23] which are reported with small experimental error shows that in most cases the agreement is better than 0.004 cm\ (it was &0.08 cm\ for the (0,0) line positions of Ref. [1]). With no recent measurements, the estimated accuracy for the (1,0), (2,1) and (3,2) lines remains &0.05 cm\. The intensity normalizations used for the (0,0) and the additional (v , v ) lines in Refs. [1,21] is very close to those reported by Copeland et al. [24], who measured relative vibrational band intensities but applied slightly di!erent absolute normalization, and to the update by Luque and Crosley [25]. We thus "nd that the line parameters of Gillis and Goldman [21] should be adequate for atmospheric and astrophysical quantitative modeling. The additional studies of OH and its isotopomers in the A&>!X%(v , v ) bands that became available in the last 15 years (e.g., [24}31]) enable further extension of the database. In particular, the studies by Stark et al. [23] and by Luque and Crosley [25] provide improvements for the line positions and transition probabilities, respectively. The work reported recently by Levin et al. [32] incorporated the same 6 bands and transition probabilities used in Gillis and Goldman [21]. Levin et al. [32] applied the results of the spectroscopic constants analysis by Stark et al. [23], but not the updated transition probabilities of Luque and Crosley [25]. We have been able to duplicate the (0,0), (1,1), (2,2) calculations by Stark et al. [23] and include them in our new line parameters calculations. This required the correction of some typographical errors in the Hamiltonian matrix elements listed in Table 3 of Stark et al. [23]. Most notably, the q term in 1% "% 2 needs to have G2x, not $x (where x"J#), and the c for " A(2)!X(2) in Table 4 should have been !1.8;10\, not !1.8;10\. Furthermore, it was necessary to increase the number of digits in the spectroscopic constants, and these were supplied for the current work by Stark from his original work for the published paper [23]. The corrections needed for the matrix elements were independently recognized by Levin et al. [32], but the published spectroscopic constants were not changed in their work, which was aimed at low resolution spectral modeling. The updated transition probabilities p(v J !v J ) and Einstein-A coe$cients A(v J !v J ) of Luque and Chidsey [25] were obtained via the LIFBASE database provided by Luque and Chidsey [33] and incorporated into our program. Comparison with our previous results [1,21] show similar A-values for most of the transitions. For J:25, the di!erences are in the range of 0.5}5% for main transitions, and 5}20% for satellite transitions. The later increase up to factor of &2 for J&35. The normalization to experiment used in the LIFBASE is essentially unchanged (686 ns instead of the 688 ns quoted above; the average of recent values presented by Cageao et al. [8] is 690$70 ns). The updated intensity parameters (Einstein A and HITRAN S) re#ect the improvement achieved in the calculated transition probabilities, as described by Luque and Crosley [25].
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227
Line intensities resulting from our calculations are shown in Figs. 1 and 2 at 296 and 4600 K, respectively. The temperature dependence of the line intensities is consistent with the exact calculation of the partition functions used by Goldman and Gillis [1] and recently reviewed by Goldman et al. [34]. The weak lines at 296 K are retained for atmospheric non-LTE applications. For the (0,0), (1,1), (2,2) transitions, calculated following Stark et al. [23] (where term values are always referenced to the X(v), F (e), J" level), we also calculated individual ground state energy values, E(v J ), by using the Coxon's constants [22] to determine the energy of the `rotationlessa vibrational levels of the X state, and the Stark et al. [23] constants for the rotational contributions. All three bands were used for the 296 K line parameters set (J "15.5), replacing the corres ponding lines calculated earlier with Coxon's constants. For the 4600 K line parameters set (J "40.5), the new (0,0), (1,1) lines were used for all J, while the (2,2) lines were used only for
J415.5, since the spectroscopic parameters for (2,2) were derived from J412.5 transitions and the accuracy of the calculated levels is diminishing rapidly in extrapolation. It should be noted that for the high-temperature line parameters set we extrapolated the A values for most v bands, beyond the dissociation limits invoked by Luque and Crosley [25,33]. The LIFBASE does not include ground state energies in the database but it provides additional (v , v ) bands which are of interest for LIF applications, covering a wider spectral range (18350}38500 cm\). A single value (0.083 cm\ atm\ at 296 K) had been in use for the air broadened half-width for all OH lines in the HITRAN databases up through 1992. This value dates back to 1979 [35]; it
Fig. 1. Line intensities and positions for the A&>(v )!X%(v ), (v , v )"(0,0), (1,1), (2,2), (1,0), (2,1), (3,2) bands of OH at 296 K. All lines with J415.5 are shown.
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Fig. 2. Line intensities and positions for the A&>(v )!X%(v ), (v , v )"(0,0), (1,1), (2,2), (1,0), (2,1), (3,2) bands of OH at 4600 K. For clarity, only lines with intensity greater than 10\ of the intensity of the strongest line have been plotted.
corresponds to the measured half-widths of the transitions around 13.4 GHz between the four levels with v"0 and J". A number of recent papers [36}40], extend the range of J values whose half-widths are measured, but also cast doubts about the accuracy of the results of Bastard et al. [35]. By averaging these measured half-widths which show the expected linearly decreasing dependence on N, we have adopted ¹"296 K half-widths for N"1,2, 4(0.097, 0.086, 0.065, and 0.053 cm\ atm\, respectively). Extending linearly to N"5 leads to the half-width of 0.040 cm\ atm\, which we have assigned to all transitions with lower levels N '4. The temperature dependence of the half-widths remains much less studied (the current HITRAN edition [16] assumes the classical value of n"0.5). Bu!a et al. [37] have calculated the broadening coe$cient for four di!erent strong pure rotation OH lines from which the average value of 0.66 was adopted. This value was used to convert the adopted half-widths at ¹"296 K to those for ¹"4600 K. It is clear that, despite the recent information available on the quantum mechanical transition and temperature dependences of the half-widths [28,38}40] (the observed rotational linewidths in (v , v )"(4,2) reported by Copeland et al. [28] are not directly applicable), the adapted half-widths are not su$cient for the wide range of line parameters needed for atmospheric and high-temperature applications. The 296 K line parameters described above will be included in the HITRAN 2000 database, but both the 296 and the 4600 K sets are already available from the authors.
J.R. Gillis et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 68 (2001) 225}230
229
Acknowledgements Research at the University of Denver was supported in part by NSF and in part by NASA. We thank J. Luque for helpful discussions regarding the LIFBASE. Acknowledgement is made to the National Center for Atmospheric Research, which is sponsored by the National Science Foundation, for computer time used in this project.
References [1] Goldman A, Gillis JR. Spectral line parameters of the A&!X% (0,0) band of OH for atmospheric and high temperatures. JQSRT 1981;25:111}35. [2] HuK bler G, Perner D, Platt U, ToK nnissen A, Ehhalt DH. Ground level OH radical concentration: new measurements by optical absorption. J Geophys Res 1984;89:1309}19. [3] McGee TJ, McIlrath TJ. Absolute OH absorption cross sections (for LIDAR measurements). JQSRT 1984;32:179}84. [4] Fennelly JA, Torr DG, Torr MR. OH A&!X%(0,0) band rotational line emission rate factors. J Geophys Res 1989;94:5183}8. [5] Mount GH. The measurement of tropospheric OH by long path absorption 1. Instrumentation. J Geophys Res 1992;97:2427}44. [6] Dorn H-P, Neuroth R, Hofzumahaus A. Investigation of OH absorption cross sections of rotational transitions in the A&>, v "0QX%, v "0 band under atmospheric conditions: implications for tropospheric long-path absorption measurements. J Geophys Res 1995;100:7397}409. [7] Mount GH, Williams EJ. An overview of the Tropospheric OH Photochemistry Experiment, Fritz Peak/Idaho Hill, Colorado, fall 1993. J Geophys Res 1997;102:6171}86. [8] Cageao RP, Ha YL, Jiang Y, Morgan MF, Yung YL, Sander SP. Calculated hydroxyl A&PX% (0,0) band emission rate factors applicable to atmospheric spectroscopy. JQSRT 1997;57:703}17. [9] Bessell MS, Hughes MG, Cottrell PL. Synthetic OH band spectra in G and K stars. Proc Astrophys Soc Australia 1984;5:547}52. [10] Bessell MS, Sutherland RS, Ruan K. Oxygen abundances in halo stars. Astrophys J 1991;383:L71}4. [11] Nissen PE, Gustafsson B, Edvardsson B, Gilmore G. Chemical composition and atmospheric parameters of metal-poor halo stars. Astron Astrophys 1994;285:440}50. [12] Israelian G, GarcmH a LoH pez RJ, Rebolo R. Oxygen abundances in unevolved metal-poor stars from near-ultraviolet OH lines. Astrophys J 1998;507:805}17. [13] Burnett CR, Burnett EB. Spectroscopic measurements of the vertical column abundance of hydroxyl (OH) in the Earth's atmosphere. J Geophys Res 1981;86:5185}202. [14] Armerding W, Spiekermann M, Comes FJ. OH multipass absorption: absolute and in situ method for local monitoring of tropospheric hydroxyl radicals. J Geophys Res 1994;99:1225}39. [15] Notholt J, SchuK tt H, Keens A. Solar absorption measurements of stratospheric OH in the UV with a Fouriertransform spectrometer. Appl Opt 1997;36:6076}82. [16] Rothman LS, Rinsland CP, Goldman A, Massie ST, Edwards DP, Flaud J-M, Perrin A, Camy-Peyret C, Dana V, Mandin J-Y, Schroeder J, McCann A, Gamache RR, Wattson RB, Yoshino K, Chance KV, Jucks KW, Brown LR, Nemtchinov V, Varanasi P. The HITRAN molecular spectroscopic database and HAWKS (HITRAN Atmospheric Workstation): 1996 edition. JQSRT 1998;60:665}710. [17] Goldman A, Schoenfeld WG, Goorvitch D, Chackerian C Jr, Dothe H, MeH len F, Abrams MC, Selby JEA. Updated line parameters for OH X%!X% (v , v ) transitions. JQSRT 1998;59:453}69. [18] Destombes JL, Marliere C, Rohart F. A unique model for the interpretation of OH vibrational ground state spectra. "-doubling hyper"ne structure, pure rotational spectrum, and A&!X%(0,0) electronic band analysis. J Mol Spectrosc 1977;67:93}116.
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[19] Chidsey IL, Crosley DR. Calculated rotational transition probabilities for the A-X system of OH. JQSRT 1980;23:187}99. [20] German KR. Direct measurement of the radiative lifetimes of the A&> (v "0) states of OH and OD. J Chem Phys 1975;62:2584}7. [21] Gillis JR, Goldman A. Line parameters update for the A&!X%(v , v ) bands of OH. University of Denver, 1982, unpublished. [22] Coxon JA. Optimum molecular constants and term values for the X%(v45) and A&>(v43) states of OH. Can J Phys 1980;58:933}49. [23] Stark G, Brault JW, Abrams MC. Fourier-transform spectra of the A&>!X% * v"0 bands of OH and OD. J Opt Soc Am 1994;B11:3}32. [24] Copeland RA, Je!ries JB, Crosley DR. Transition probabilities in OH A&>!X% : bands with v "0 and 1, G v "0 to 4. Chem Phys Lett 1987;138:425}30. [25] Luque J, Crosley DR. Transition probabilities in the A&>!X% electronic system of OH. J Chem Phys G 1998;109:439}48. [26] Lin S-R, Lee S-T, Lee Y-P. The S lines of the A&>(v "1)QX%(v "0) transitions of OH and OD. JQSRT 1987;38:163}6. [27] Takubo Y, Miyata Y, Amemiya K, Yamamoto M. Magneto-optic spectra of the A&>!X% transition of OH. G J Chem Phys 1990;93:176}82. [28] Copeland RA, Je!ries JB, Crosley DR. The OH A&>!X% (4,2) band: line positions and linewidths. J Mol G Spectrosc 1990;143:183}5. [29] Coxon JA, Sappey AD, Copeland RA. Molecular constants and term values for the hydroxyl radical, OH: the X%(v"8,12), A&>(v"4!9), B&>(v"0,1), and C&>(v"0,1) states. J Mol Spectrosc 1991;145:41}55. [30] Cheung AS-C, Chan CM-T, Sze NS-K. The A&>!X% bands of OH. J Mol Spectrosc 1995;174:205}14. [31] Slanger TG, Copeland RA. Energy transfer, spectroscopy, and atmospheric signi"cance of excited O , NO and OH. in: J.R. Barker editor. Progress and Problems in Atmospheric Chemistry, World Scienti"c, Singapore, 1995, Chapter 13. [32] Levin DA, Laux CO, Kruger CH. A general model for the spectral calculation of OH radiation in the ultraviolet. JQSRT 1999;61:377}92. [33] Luque J, Crosley DR. LIFBASE: Database and spectral simulation program (Version 1.5). SRI International Report MP 99-009, 1999. [34] Goldman A, Gamache RR, Perrin A, Flaud J-M, Rinsland CP, Rothman LS. HITRAN partition functions and weighted squares of the transition moments. JQSRT 2000;66:456}86. [35] Bastard D, Bretenoux A, Charru A, Picherit F. Determination of mean collision cross sections of free radical OH with foreign gases. JQSRT 1979;21:369}72. [36] Khayar A, Bonamy J. Calculation of mean collision cross sections of free radical OH with foreign gases. JQSRT 1982;28:199}212. [37] Bu!a G, Tarrini O, Inguscio M. Predictions for collisional broadening of far-infrared OH rotational lines of atmospheric interest. Appl Opt 1987;26:3066}8. [38] Chance KV, Jennings DA, Evenson KM, Vanek MD, Nolt IG, Radostitz JV, Park K. Pressure broadening of the 118.455 cm\ rotational lines of OH by H , He, N , and O . J Mol Spectrosc 1991;146:375}80. [39] Schi!man A, Nesbitt DJ. Pressure broadening and collisional narrowing in OH(v"1Q0) rovibrational transitions with Ar, He, O , and N . J Chem Phys 1994;100:2677}89. [40] Park K, Zink LR, Evenson KM, Chance KV, Nolt IG. Pressure broadening of the 83.869 cm\ rotational lines of OH by N , O , H , and He. JQSRT 1996;55:285}7.
Note
Line parameters for the A&>!X% bands of OH James R. Gillis , Aaron Goldman *, Glenn Stark, Curtis P. Rinsland Boeing Space & Communication Group, P.O. Box 3999 MS 8H-05, Seattle, WA 98124-2499, USA Department of Physics and Astronomy, University of Denver, 2112 E Wesley Avenue, Denver, CO 80208, USA Department of Physics, Wellesley College, Wellesley, MA 02481, USA Atmospheric Science Division, NASA Langley Research Center, Hampton, VA 23681-2199, USA Received 6 December 1999
Abstract Updated line parameters, including line positions and intensities, have been generated for the six strongest A&>(v )!X% (v ) bands of OH, i.e., v !v "0,#1, v "0, 1, 2, applicable to atmospheric and high G temperatures. Results from recent laboratory measurements and theoretical studies have been incorporated into the calculations. Tables of line parameters are available for 296 and 4600 K. 2000 Elsevier Science Ltd. All rights reserved.
The OH line parameters for the A&>(v "0)!X% (v "0) band generated almost 20 years G ago by Goldman and Gillis [1] have been used routinely in atmospheric and astrophysical studies (e.g., [2}12] and references therein). Other atmospheric UV studies of OH have used very similar values, e.g., Burnett and Burnett [13], Armerding et al. [14], Notholt et al. [15] and references therein. While UV}VIS line parameters are now a formal part of the HITRAN database [16], these OH lines have not been included yet in the database. The IR OH line parameters have been updated extensively in the recent work of Goldman et al. [17]. The calculations by Goldman and Gillis [1] were based on the spectroscopic constants of Destombes et al. [18] for energy levels and line positions, the relative Einstein coe$cients A(v J !v J ) of Chidsey and Crosley [19], and on the intensity normalization according to the rotationless (N "0) v "0 lifetime as measured by German [20], q "(0.688$0.007);10\ s. The line positions were estimated to be accurate to better than 0.1 cm\. In subsequent, unpublished, calculations, Gillis and Goldman [21] revised the A&>(v "0)!X%(v "0) line parameters calculations, using the spectroscopic constants of Coxon [22], with the previous [1] intensity normalization. The accuracy of the new line positions * Corresponding author. Tel.: #1-303-871-2238; fax: #1-303-871-4405. 0022-4073/00/$ - see front matter 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 2 - 4 0 7 3 ( 0 0 ) 0 0 0 1 1 - X
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was estimated to be better than 0.01 cm\. The line parameters for the A&>(v )!X%(v ), (v , v )"(1,1), (2,2), (1,0), (2,1), (3,2), were also calculated in that work. According to the recent work of Cageao et al. [8], the Goldman and Gillis (0,0) line parameters remain the adopted database. It was recognized, however, by Cageao et al. [8] that a signi"cant improvement in the (0,0), (1,1), (2,2) line positions was provided by the high-resolution FTS work of Stark et al. [23], but that no signi"cant change in the intensity normalization can be concluded from the available publications. Comparing (0,0), (1,1) and (2,2) line positions of Gillis and Goldman [21] with those lines from Stark et al. [23] which are reported with small experimental error shows that in most cases the agreement is better than 0.004 cm\ (it was &0.08 cm\ for the (0,0) line positions of Ref. [1]). With no recent measurements, the estimated accuracy for the (1,0), (2,1) and (3,2) lines remains &0.05 cm\. The intensity normalizations used for the (0,0) and the additional (v , v ) lines in Refs. [1,21] is very close to those reported by Copeland et al. [24], who measured relative vibrational band intensities but applied slightly di!erent absolute normalization, and to the update by Luque and Crosley [25]. We thus "nd that the line parameters of Gillis and Goldman [21] should be adequate for atmospheric and astrophysical quantitative modeling. The additional studies of OH and its isotopomers in the A&>!X%(v , v ) bands that became available in the last 15 years (e.g., [24}31]) enable further extension of the database. In particular, the studies by Stark et al. [23] and by Luque and Crosley [25] provide improvements for the line positions and transition probabilities, respectively. The work reported recently by Levin et al. [32] incorporated the same 6 bands and transition probabilities used in Gillis and Goldman [21]. Levin et al. [32] applied the results of the spectroscopic constants analysis by Stark et al. [23], but not the updated transition probabilities of Luque and Crosley [25]. We have been able to duplicate the (0,0), (1,1), (2,2) calculations by Stark et al. [23] and include them in our new line parameters calculations. This required the correction of some typographical errors in the Hamiltonian matrix elements listed in Table 3 of Stark et al. [23]. Most notably, the q term in 1% "% 2 needs to have G2x, not $x (where x"J#), and the c for " A(2)!X(2) in Table 4 should have been !1.8;10\, not !1.8;10\. Furthermore, it was necessary to increase the number of digits in the spectroscopic constants, and these were supplied for the current work by Stark from his original work for the published paper [23]. The corrections needed for the matrix elements were independently recognized by Levin et al. [32], but the published spectroscopic constants were not changed in their work, which was aimed at low resolution spectral modeling. The updated transition probabilities p(v J !v J ) and Einstein-A coe$cients A(v J !v J ) of Luque and Chidsey [25] were obtained via the LIFBASE database provided by Luque and Chidsey [33] and incorporated into our program. Comparison with our previous results [1,21] show similar A-values for most of the transitions. For J:25, the di!erences are in the range of 0.5}5% for main transitions, and 5}20% for satellite transitions. The later increase up to factor of &2 for J&35. The normalization to experiment used in the LIFBASE is essentially unchanged (686 ns instead of the 688 ns quoted above; the average of recent values presented by Cageao et al. [8] is 690$70 ns). The updated intensity parameters (Einstein A and HITRAN S) re#ect the improvement achieved in the calculated transition probabilities, as described by Luque and Crosley [25].
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227
Line intensities resulting from our calculations are shown in Figs. 1 and 2 at 296 and 4600 K, respectively. The temperature dependence of the line intensities is consistent with the exact calculation of the partition functions used by Goldman and Gillis [1] and recently reviewed by Goldman et al. [34]. The weak lines at 296 K are retained for atmospheric non-LTE applications. For the (0,0), (1,1), (2,2) transitions, calculated following Stark et al. [23] (where term values are always referenced to the X(v), F (e), J" level), we also calculated individual ground state energy values, E(v J ), by using the Coxon's constants [22] to determine the energy of the `rotationlessa vibrational levels of the X state, and the Stark et al. [23] constants for the rotational contributions. All three bands were used for the 296 K line parameters set (J "15.5), replacing the corres ponding lines calculated earlier with Coxon's constants. For the 4600 K line parameters set (J "40.5), the new (0,0), (1,1) lines were used for all J, while the (2,2) lines were used only for
J415.5, since the spectroscopic parameters for (2,2) were derived from J412.5 transitions and the accuracy of the calculated levels is diminishing rapidly in extrapolation. It should be noted that for the high-temperature line parameters set we extrapolated the A values for most v bands, beyond the dissociation limits invoked by Luque and Crosley [25,33]. The LIFBASE does not include ground state energies in the database but it provides additional (v , v ) bands which are of interest for LIF applications, covering a wider spectral range (18350}38500 cm\). A single value (0.083 cm\ atm\ at 296 K) had been in use for the air broadened half-width for all OH lines in the HITRAN databases up through 1992. This value dates back to 1979 [35]; it
Fig. 1. Line intensities and positions for the A&>(v )!X%(v ), (v , v )"(0,0), (1,1), (2,2), (1,0), (2,1), (3,2) bands of OH at 296 K. All lines with J415.5 are shown.
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Fig. 2. Line intensities and positions for the A&>(v )!X%(v ), (v , v )"(0,0), (1,1), (2,2), (1,0), (2,1), (3,2) bands of OH at 4600 K. For clarity, only lines with intensity greater than 10\ of the intensity of the strongest line have been plotted.
corresponds to the measured half-widths of the transitions around 13.4 GHz between the four levels with v"0 and J". A number of recent papers [36}40], extend the range of J values whose half-widths are measured, but also cast doubts about the accuracy of the results of Bastard et al. [35]. By averaging these measured half-widths which show the expected linearly decreasing dependence on N, we have adopted ¹"296 K half-widths for N"1,2, 4(0.097, 0.086, 0.065, and 0.053 cm\ atm\, respectively). Extending linearly to N"5 leads to the half-width of 0.040 cm\ atm\, which we have assigned to all transitions with lower levels N '4. The temperature dependence of the half-widths remains much less studied (the current HITRAN edition [16] assumes the classical value of n"0.5). Bu!a et al. [37] have calculated the broadening coe$cient for four di!erent strong pure rotation OH lines from which the average value of 0.66 was adopted. This value was used to convert the adopted half-widths at ¹"296 K to those for ¹"4600 K. It is clear that, despite the recent information available on the quantum mechanical transition and temperature dependences of the half-widths [28,38}40] (the observed rotational linewidths in (v , v )"(4,2) reported by Copeland et al. [28] are not directly applicable), the adapted half-widths are not su$cient for the wide range of line parameters needed for atmospheric and high-temperature applications. The 296 K line parameters described above will be included in the HITRAN 2000 database, but both the 296 and the 4600 K sets are already available from the authors.
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Acknowledgements Research at the University of Denver was supported in part by NSF and in part by NASA. We thank J. Luque for helpful discussions regarding the LIFBASE. Acknowledgement is made to the National Center for Atmospheric Research, which is sponsored by the National Science Foundation, for computer time used in this project.
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