THE UNIVERSITY OF MICHIGAN COLLEGE OF ENGINEERING High Altitude Engineering Laboratory Departments of Aerospace Engineering Meteorology and Oceanography Quarterly Report HIGH ALTITUDE RADIATION MEASUREMENTS 1 February 1972 - 30 April 1972 Fred L. Bartman ORA PROJECT 03635 0 under contract with NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CONTRACT No. NSR 23-005-376 WASHINGTON, D. C. administered through OFFICE OF RESEARCH ADMINISTRATION ANN ARBOR May 1972

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Table of Contents Pag Abstract I. Introduction 1 II. High Resolution Measurements (L. W. Chaney) 1 III. Analysis of High Resolution C02 Spectra (S. R. Drayson) 2 IV. Medium Resolution Measurements of the 9. 6 gm Absorption Band of 03 (L. T. Loh and P. A. Titus) 2 V. Analysis of the Medium Resolution 9. 6 pm 03 Spectra (W. R. Kuhn) 5 VI. Study of the Spectra of CO2 Isotopes (J. B. Russell) 8 VII. Plans for future work 8 ge iii

Abstract This report summarizes project activity during the period 1 February 1972 to 30 April 1972. Results of the analysis of high resolution spectra of CO2 in the 15 gm region are given in 2 tables. Modifications of the White Cell used for medium resolution 9. 6pm 03 data are described and results with the modified White Cell are given. Technical Reports on the work already carried out are being prepared.

I. Introduction This is the 10th Quarterly Progress Report on Contract No. NSR 23-005-376, covering the period 1 February to 30 April 1972. The project effort during this time interval was divided among the following tasks. A. High resolution measurements (L. W. Chaney) B. Analysis of High Resolution CO2 Spectra (S. R. Drayson) C. Medium Resolution Measurements of the 9. 6pm Absorption Band of 03 (L. T. Loh and P. A. Titus) D. Analysis of the Medium Resolution 9. 6 um 03 Spectra (W. R. Kuhn). E. Study of the Spectra of CO2 Isotopes (J. B. Russell). II. High Resolution Measurements (L. W. Chaney) The high resolution measurements of the 15psm and 4. 3um bands of CO2 have now been completed. During this time interval the instrument was used for measurements of 2. 3pm and 4. 6/m bands of CO on another contract. After this work was completed the instrument was turned back over to the Willow Run Laboratory personnel who are responsible for the instrument for use on one of their contracts. Arrangements are being made to use the equipment for high resolution measurements of 03 starting in approximately February 1973. A technical report summarizing the high resolution measurements has been started. The report will describe experimental details and contain analog records of the data taken. 1

III. Analysis of High Resolution CO2 Spectra (S. R. Drayson) Preparation of a technical report on the analysis of the high resolution spectra of CO2 in the 15/pm region is continuing. Tables 1 and 2 summarize the most important results obtained. The spectra have also been used to estimate the intensities of some of the weaker bands, while others remain to be completed (See Table 2). Line positions ai have been calculated in preparation for tthe analysis of the high resolution spectra taken in this region. Comparison of experimental and theoretical spectra should yield good estimates of band intensities of some of the weaker bands whose intensities have not previously beenv estimated. IV. Medium Resolution Measurements of the 9. 6pm Absorption Band of 0 (L. T. Loh and P. A. Titus). 3 The Perkin-Elmer #221 spectrophotometer developed operational problems in February, a gradual loss of detector sensitivity and erratic action of the slit system. The bad detector was repl good thermocouple made by Charles M. Reeder & Company Michigan. The cause of slit trouble was traced to 2 loose set screws on the shaft of slit servo-motor. It was fixed. The electron circuits and the optical components were also checked and aligned. The White cell which contains the 03 sample was coated with teflon. Mixing of the 03 mixture was improved by the installation of a stirring device. The teflon coating was applied after covering all the mirrors with thin polyethylene and the KBr windows with several layers of lens tissue 2

- Table 1: Vibrational and rotational constants for CO2. All units are cm. Isotope 626 626 626 626 626 626 626 626 626 636 636 636 628 628 Level 000:0 010:1 (100:0)I (100:0)II 020:2 (110:1)I (110:1 )II 030:3 001:0 000':0* 010:1 020:2 000:0* 010:1 Vibrational Energy 0. 0 667.381 1388. 185 1285. 410 1335.131 2076.855 1932. 473 2003. 238 2349. 144 0. 0 648. 4816 1297. 269 0. 0 662. 368 B c.3902196.3906393.3901878.3904812.3916723.3904025.3907321.3923879.3'871396.3902350.3905975.3916147-.3681640.3685961.I Rotational Constants B D d c 3902196 13.31x10-8 3912539 13.49x108 3901878 11.42x108 3904812 15.63xlO8 3916646 13.97x108 3913282 12.28x108 3916753 14.37x108 -8 3923811 13.88x108 3871396 13.24x108 3902350 13.10x108 -8 3912357 12.90x108 -8 3916032 13.74x108 3681640 11. 10x108 3690900 12.08x10 Dd 13.31xl08 13.51xl108 11.42x108 15. 63x108 13. 64x108 11.81x 108 15. 26x108 13.90x108 13. 24x108 13. 10x108 -8 12.93xI08 13. 14x108 1. 10x10-8 12. 08x108 I.. * constants for ground states of isotopic molecules from W. S. Benedict (private communication)

Table 2: Band centers and intensities of CO bands between 12 and 18pim. Band centers in cml1, intensities ire at 300K in units cm-l (atm cm). 300K. Values in parenthesies are less certain. Band 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 4 1 1 Upper 010:: 1 (100:0)1 ( 1oo:O)I 020:2 (110:1)11 (110:1)I (110:1l)II (110:1)I 030:3 (110:1)11 (120:2)II (120:2)I (120:2)1 (200:O)II (110:1)I 010:1 020:2 010:1 010:1 Lower 000:0 010:1 010:1 010:1 (100: 0)11 (100:0.)1 (l Oo:O)II 020:2 020:2 020:2 (100:O)I 030:3 030:3 (110:1)II (110:1)11 (100:0)I 000:0 010:1' 000:0 000:0 Isotope Center Intensity 626 667. 381 194. 0 626 618. 029 4. 27 626 620. 805 5. 0 626 667. 751 15. 0 626 647.063 0.7 626 791. 446 0. 022 626 597. 342 0. 14 626 741. 724 0. 144 626 668. 107 0. 85 626 544. 288 0.01 626 (581. 67) 0 0084 626 (757. 52) 0. 009 626 (828. 28) (0. 0002) 626 (738. 64) (0. 014) 626 688. 670 0. 3 636 648.482 * 636 648. 787 * 628 662.368* 627 664. 72* * intensities for isotopes are obtained by multiplying the 626 intensities by the relative abundancies of the isotopic species. 4

and two layers of masking tape. The teflon spray was type GS-3 made by RAM Chemicals of Gardena, California. Altogether 8 lbs. of the spray were used, 4 lbs. on the wall of the cover, and 4 lbs. on the remaining surfaces. With the coating, the rate of loss of ozone was decreased particularly after the first and the second runs. The stirring device wats used twice during the runs of spectra #87 to 92. It appeared to be leak-tight and free from outgassing. The vacuum side of this device was made of ozone resisting materials. The. vacuum seal to the stirrer shaft was provided by a compressed viton 0-ring with Ascolube silicone grease made by Asco Manufacturing Company, Pompano Beach, Florida. With the teflon coating and the stirring device, the sample White cell could be charged with a quantity of ozone and additional oxygen added to adjust the total pressure. The cell could be valved off and its contents mixed by the stirrer. The ozone will!stay almost constant for the time of a run. Twelve ozone scans were taken, #81- 92, after the modification, for low ozone mass-path, with the White cell path length set to 400 cm. Runs #89-92 were made with the use of stirring device. V. Analysis of the Medium Resolution 9. 6/m 03 Spectra (W. R. Kuhn) As discussed in the last quarterly report our 9. 61m ozone absorptivities were about 15 % larger than those of Walshaw (1957). Possible sources for the discrepancy were a non uniform mixing of the ozone in the cell, and interaction of ozone with the cell walls. In order to minimize these effects the cell was teflon coated, and a stirring device was installed. Additional measurements were then made and some typical 5

results are presented in Table 3. For this work, the 9. 6gm band was considered to extend from 9. 35 to 11. 35gum. The first five runs were made after the cell had been coated; runs 6 and 7 included the fan, but inoperative, while in the last four runs the fan operated for 10 sec periods with 15 sec intermissions. Table 3: Comparison of 9.6/ absorptivities with Walshaw's empirical formula for selected pressures and mass paths. Absorptivity (cm ) Pressure (mmHg) 5'5 6. 1 15. 1 15. 2 15. 4 30. 5 31. 0 31. 3 47. 6 47. 7 47.8 Mass Path (cm STP) 0. 072 0. 058 0. 184 0. 177 0. 168 0. 680 0. 630 0. 592 0. 966 0. 937 0. 906 Present (9. 6 tm) 9. 05 8. 30 20. 6 20. 3 20. 0 47. 1 44. 5 43. 3 56. 3 55.8 55.2 Walshaw (9. 6A.m) 9. 3 7. 6 20. 3 20. 1 18. 8 46. 6 45. 4 44. 3 57. 0 58. 5 57. 8 Present- Walshaw Present 0. 12 0. 092 0.015 0. 01 0. 064 0.011 -0. 022 -0. 023 -0. 012 -0. 046 -0. 045 Walshaw, C. D., 1957: Quart. J. Roy. Meteor. Soc. 83, 315. 6

These latest results show considerably better agreement with those from Walshaw's empirical expression, the differences1 being only on the order of a few percent except at very low pressures and mass paths. Note also that most of the discrepancy with Walshaw was apparently due to interaction of ozone with the cell, i. e., there was no apparent better agreement with his data for the last four runs when the stirring device was operating than in the first five runs when it was not. It is felt that our measurements substantiate Walshaw's empirical expression. His r. m. s. value for the difference between the observed and measured absorptivities, expressed as a percentage of the observed band area is 2. 4, which compares favorably with those results in Table 3. Although we feel Walshaw's empirical formula adequately represents the absorptivity over the range for which it was intended, there is a need for additional measurements for conditions which are found in the stratosphere, i.e., for low pressures and mass paths. For example, the 9. 6Am band makes its maximum contribution to the flux divergence near the stratopause where a five km thick layer would contain about 0. 005 atm. cm ozone at a pressure of about 0. 8 mm Hg. These values are well below those used by Walshaw (e. g. minimum pressures and mass paths are 11. 2 mm Hg with 0. 026 atm cm, and 0. 00278 atm cm at 728 mm Hg), and while it is doubtful if our measurements could be made for these low pressures and mass paths nevertheless we should be able to extend Walshaw's results. Also Walshaw does not include the 9Mm band in his empirical formula. For atmospheric work, however, one requires the total absorption in the 9im region. Although small in comparison to the absorptivity of the 9. 6pm 7

band (e. g. at 27 mm Hg and 0. 15 atm cm, the absorptivity from the 9 m band is about 4% that of the 9. 6 band), present levels of sophistication for radiative transfer calculations in the stratosphere dictate its inclusion. VI. Study of the Spectra of CO2 Isotopes (J. B. Russell). The work on the isotopic spectra of CO2, the PhD dissertation of J. B. Russell, is being done in absentia. Several computing errors were discovered and corrected after runring the programs written at U. S. Naval Avionics Facility, Indianapolis (NAFI) on the University of Michigan Computer..13 16 Analysis of the C 02 isotope is continuing. VII. Plans for Future Work. The work for the remainder of this contract year will consist of medium resolution measurements of 03 at temperatures lower than room temperature, of the analysis of existing 03 and CO2 data and of the writing of reports on the work already completed. 8

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