- Email: [email protected]
Terahertz spectroscopy of water in its second triad
Journal of Molecular Spectroscopy 288 (2013) 7–10
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Spectroscopy journal homepage: www.elsevier.com/locate/jms
Note
Terahertz spectroscopy of water in its second triad Shanshan Yu ⇑, John C. Pearson, Brian J. Drouin Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, United States
a r t i c l e
i n f o
Article history: Received 27 February 2013 Available online 9 April 2013 Keywords: High temperature water THz spectroscopy DC discharge
a b s t r a c t Terahertz absorption spectroscopy was employed to measure rotational transitions of water in its second triad 3m2 ; m1 þ m2 and m3 þ m2 . Highly excited water molecules were created with a DC discharge, which allowed observation of transitions with lower state energies up to 5939 cm1. In the 0.5–2.0 THz region, 38 pure rotational transitions in the second triad were observed with MW accuracy for the first time. Additionally, 91 new rotational and ro-vibrational transitions within the ground state, m2 , and the first triad (2m2 ; m1 and m3 ) were measured with multiplier chains covering the 1.3–2.0 THz region. Ó 2013 Elsevier Inc. All rights reserved.
Water provided the first coherent source of THz radiation once its laser action was discovered in 1964 [1]. The general features of the water spectrum have been exceptionally well sorted out after decades of high resolution spectroscopy [2]. However, the extremely non-rigid nature of the water molecule has thus far defied analysis of its Doppler limited frequency measurements to within experimental accuracy. As such, it is still necessary to frequency measure water transitions. The current effort is necessary to support the study of oxygen-rich asymptotic giant branch stars, where water observations have been detected in a number of highly excited vibrational states [3]. Water has three vibrational modes, a symmetric stretch m1 , a bend m2 and an anti-symmetric stretch m3 . We denote these modes as ðv 1 ; v 2 ; v 3 Þ where the commas are omitted for quanta less than 10. The present work follows our previous study [4] in which the rotational and ro-vibrational transitions of water in the ground state, (0 1 0), and the first triad (0 2 0), (1 0 0) and (0 0 1) were measured and analyzed with two different methods. In this study, the pure rotational transitions in the second triad (0 3 0), (1 1 0) and (0 1 1) of water were measured with terahertz absorption spectroscopy for the first time. These three vibrational levels lie high in energy, with vibrational energies of 4667, 5235, 5331 cm1, respectively. In addition, 91 new transitions in the ground state, (0 1 0), and the first triad (0 2 0), (1 0 0) and (0 0 1) were measured with our new multiplier chains covering the 1300–2000 THz region. Since the previous paper [4] provided a detailed analysis and the present data for the lowest five states is consistent with residuals from the previous work, no additional fitting of line positions was performed. The new data in the second triad are too limited to have a significant impact on molecular constants. As a result, no data analysis, i.e., fit of the measured line positions to ⇑ Corresponding author. E-mail address: [email protected] (S. Yu). 0022-2852/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jms.2013.03.011
Hamiltonian models, was carried out and only the measured line positions are reported for the benefit of velocity resolved astronomical spectroscopy. There is a vast literature dealing with experimental investigations of the second triad of water and we refer readers to the latest four papers [2,5–7] for details on previous studies. The obtained maximum J was 18 in Toth [5], 17 in Mikhailenko et al. [6], 18 in Coudert et al. [7]. To guide our experimental search for the line positions of pure rotation transitions in the second triad, we used the predictions from a global analysis by Coudert [8], which is based on the Bending-Rotation approach [9–12] and is still in progress. The frequency multiplied submillimeter spectrometer (FMSS) used for the measurements is described in Ref. [13], with eight multiplier chains covering the 290–1230 and 1575–1626 GHz ranges with some small gaps in between. The present work involves four new multiplier chains covering the 1300–2000 GHz region [14,15]. The measurements were carried out with a 1.2-m-long DC discharge cell and with water pressures ranging from 100 mtorr to 180 mtorr. Typical discharge currents were 350 mA and the voltage across the electrodes was about 3 kV. Note that our frequency positions were not corrected for pressure shifts. The uncertainties were estimated to be between 50 and 500 kHz. Fig. 1 shows the observed J 0K 0a ;K 0c J 00K 00a ;K 00c ¼ 63;3 62;4 rotational line in the (0 1 1) vibrational state. A few H2O2 transitions were also observed while we searched around the predicted H2O transition frequencies. Table 1 lists the assignment, observed position, experimental uncertainty, difference from the Bending-Rotation model in Ref. [8], and lower state energy for the newly measured 38 pure rotational transitions of water in the second triad (0 3 0), (1 1 0) and (0 1 1). The model results differ from the observed frequencies from 19 MHz to 14 MHz. The observed JðMaxÞ was 6 and the observed highest energy level was at 5939 cm1. We have searched but
8
S. Yu et al. / Journal of Molecular Spectroscopy 288 (2013) 7–10
(011) 63, 3 − 62, 4
1887270
1887290
1887310
1887330
1887350
188737 0
Frequency (MHz) Fig. 1. The observed ðv 1 v 2 v 3 Þ ¼ ð0 1 1Þ, J0K 0a ;K 0c J00K 00a ;K 00c ¼ 63;3 62;4 pure rotational water line together with severe baseline. The lower state energy of this transition is 5939 cm1. The integration time was 1.5 s on each point. An experimental uncertainty of 100 kHz was assigned to the measured line position.
failed to observe transitions with larger J, which has led us to believe that in Fig. 1 of our previous study [4] the tentative assignment of the 1151447 MHz line to J ¼ 12 of (0 3 0)–(1 1 0) is in question. The DC discharge only modestly enhances the rotational
temperature, while it provides a significant enhancement of the vibrational temperature. The result is that only the lowest rotational levels in excited vibrational states are sufficiently populated to observe. These new measurements were added to the compiled list of microwave water transitions given in our previous work [4] and the updated list is given in the ‘‘MWwaterlines.txt’’ file in the Supplemental Material of this note. Table 2 lists the assignment, observed position, experimental uncertainty, difference from the Bending-Rotation model in Ref. [4], and lower state energy for the newly measured 91 rotational and ro-vibrational transitions of water in the ground state, m2 ¼ 1 and the first triad (0 2 0), (1 0 0), (0 0 1). Differences up to 10 MHz were found between the model results and the observed frequencies. Laser action was observed at 532 644 GHz and 1 312 041 GHz. These new measurements were also added to the ‘‘MWwaterlines.txt’’ file in the Supplemental Material of this note. To validate existing datasets, 52 previously measured transitions in the five lowest states were also re-measured. These re-measured frequencies were also included in the ‘‘MWwaterlines.txt’’ file in the Supplemental Material. We re-assessed experimental uncertainties for previously reported frequencies based on repeated measurements. All the remeasured positions agree well with previous values, except for the 105;6 —96;3 and 106;5 —107;4 lines of the (0 1 0) state. These two lines were measured previusly by the Cologne group in our previous work [4]. The JPL-measured vs. Cologne-measured values for these two lines are 1866271.866(50) vs. 1866269.960(300) and 1871695.115(50) vs.
Table 1 Assignment, observed position, experimental uncertainty, difference from the Bending-Rotation model in Ref. [8], and lower state energy for the newly measured 38 pure rotational transitions of water in the second triad (0 3 0), (1 1 0) and (0 1 1). J0K 0a ;K 0c
v 01 v 02 v 03
J00K 00a ;K 00c
v 001 v 002 v 003
Observed (MHz)
Unc. (MHz)
O:—C: (MHz)
E00 (cm1)
11;1 11;1 11;1 11;0 11;0 11;0 21;2 21;2 20;2 20;2 21;1 21;1 21;1 22;0 22;0 22;1 22;1 30;3 30;3 30;3 31;2 31;2 31;2 32;1 22;0 41;3 41;3 41;3 41;3 41;3 42;2 42;2 32;1 52;3 52;3 62;4 62;4 63;3
030 110 011 030 110 011 110 011 110 011 030 110 011 110 011 110 011 030 110 011 030 110 011 110 030 030 110 011 110 011 110 011 030 110 011 110 011 011
00;0 00;0 00;0 10;1 10;1 10;1 10;1 10;1 11;1 11;1 20;2 20;2 20;2 21;1 21;1 21;2 21;2 21;2 21;2 21;2 30;3 30;3 30;3 31;2 31;3 32;2 32;2 32;2 40;4 40;4 41;3 41;3 41;4 51;4 51;4 61;5 61;5 62;4
030 110 011 030 110 011 110 011 110 011 030 110 011 110 011 110 011 030 110 011 030 110 011 110 030 030 110 011 110 011 110 011 030 110 011 110 011 011
1519493.285 1174679.308 1154046.217 988270.194 637714.013 614348.435 1711840.578 1695031.030 894833.079 928596.443 1199093.531 839546.907 822484.021 1436857.865 1363583.637 1896020.257 1826929.314 1375728.372 1624633.034 1655545.358 1559052.800 1194827.872 1189488.320 1350535.743 1062841.460 1044018.072 1855413.208 1919778.551 1719294.989 1727231.121 1406976.895 1341289.223 873631.048 1560690.153 1543549.888 1923327.454 1936356.238 1887327.909
0.100 0.300 0.100 0.100 0.200 0.200 0.100 0.200 0.300 0.300 0.200 0.100 0.100 0.300 0.200 0.200 0.300 0.200 0.200 0.300 0.100 0.100 0.100 0.100 0.300 0.200 0.300 0.100 0.200 0.100 0.300 0.100 0.300 0.100 0.200 0.100 0.200 0.100
3.045 2.876 2.475 3.856 3.063 2.193 3.211 3.279 9.241 6.304 2.201 0.038 0.036 8.203 5.131 2.430 0.010 19.458 8.769 6.399 0.410 4.288 3.385 7.251 18.554 10.881 13.340 5.192 6.915 6.736 0.281 4.045 11.691 0.112 5.927 0.069 8.240 7.095
4666.7892 5234.9750 5331.2671 4690.5797 5258.3994 5354.8709 5258.3994 5354.8709 5274.1582 5369.7619 4737.2026 5304.0063 5400.7367 5332.0105 5428.1719 5315.5003 5411.4109 4759.0232 5315.5003 5411.4109 4804.9133 5369.6920 5466.6342 5409.5470 4820.7622 4926.8619 5449.0299 5544.2486 5453.5701 5550.6713 5510.9194 5608.2857 4902.1302 5634.1209 5731.9161 5776.7913 5874.7467 5939.3363
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S. Yu et al. / Journal of Molecular Spectroscopy 288 (2013) 7–10
Table 2 Assignment, observed position, experimental uncertainty, difference from the Bending-Rotation model in Ref. [4], and lower state energy for the newly measured 91 rotational and ro-vibrational transitions of water in the ground state, m2 ¼ 1 and the first triad (0 2 0), (1 0 0), (0 0 1). J0K 0a ;K 0c 84;4 62;4 107;3 31;2 82;7 53;2 53;3 147;8 42;3 72;6 133;11 64;3 72;6 11;1 107;3 31;2 74;4 62;5 145;10 52;3 137;7 52;3 94;5 62;5 64;3 41;4 93;7 74;3 63;3 1210;2 1210;3 93;7 41;3 118;4 118;3 30;3 22;1 53;2 113;8 72;5 73;5 66;1 64;2 30;3 104;7 164;12 123;10 30;3 53;3 63;3 42;2 104;7 72;6 103;8 32;1 155;11 63;3 73;4 73;4 62;4 129;4 129;3 62;4 43;1 84;5 63;4 32;2 52;3 105;6 52;3
v 01 v 02 v 03 020 001 010 020 020 100 001 000 001 020 010 100 001 020 000 020 001 100 000 001 000 100 020 001 100 001 020 001 100 000 000 020 020 000 000 020 001 001 010 010 100 020 100 100 000 000 010 001 000 001 020 020 001 020 020 000 100 001 100 100 000 000 001 001 100 100 001 001 100 020
J 00K 00a ;K 00c 75;3 71;7 98;2 22;1 73;4 44;1 44;0 154;11 33;0 63;3 124;8 62;4 63;3 00;0 98;2 30;3 65;1 53;2 152;13 51;4 144;10 51;4 85;4 53;2 54;2 41;3 80;8 65;2 54;2 1111;1 1111;0 84;4 32;2 109;1 109;2 21;2 21;2 52;3 122;11 81;8 64;2 62;4 54;1 21;2 111;10 173;15 114;7 21;2 60;6 62;4 41;3 95;4 64;3 94;5 31;2 162;14 62;4 72;5 72;5 61;5 1110;1 1110;2 61;5 42;2 75;2 70;7 31;3 44;0 103;7 51;4
v 001 v 002 v 003 020 001 010 020 020 100 001 000 001 020 010 001 001 020 000 020 001 100 000 001 000 100 020 001 001 100 100 001 100 000 000 020 020 000 000 020 001 001 010 010 100 001 001 100 000 000 010 001 000 001 020 020 100 020 020 000 100 001 100 100 000 000 001 001 100 100 001 100 001 020
Observed (MHz) a
532644.463 533240.158 548868.742 554055.105 566500.881 567221.559 583211.504 591693.639 591977.103 610798.188 1088558.746 1312041.828a 1328798.943 1332979.607 1335984.742 1360579.357 1361104.994 1362642.145 1378163.986 1381195.839 1386269.187 1390554.341 1431808.865 1451322.977 1474751.265 1482735.850 1486471.369 1487702.793 1511691.386 1516088.633b 1516088.633b 1517769.992 1525774.148 1529130.871 1529245.865 1538690.835 1563748.988 1564363.252 1638667.804 1646633.295 1675143.165 1689240.474 1690312.124 1693083.943 1693470.368 1694135.960 1695430.101 1716391.671 1716956.789 1718695.008 1719735.763 1722884.590 1735452.117 1737030.079 1742476.965 1753305.893 1759388.834 1760795.953 1766550.041 1776637.616 1794630.094 1794648.504 1797024.539 1808972.444 1815476.292 1820502.441 1831064.289 1833907.958 1839396.686 1842750.067
Unc. (MHz)
O:—C: (MHz)
E00 (cm1)
0.050 1.000 0.200 0.200 0.100 0.100 0.100 0.200 0.200 0.500 0.200 0.100 0.200 0.050 0.050 0.050 0.200 0.100 0.050 0.050 0.300 0.050 0.300 0.500 0.500 0.500 0.300 0.500 0.300 0.200 0.200 0.200 0.100 0.050 0.100 0.050 0.050 0.050 0.500 0.100 0.200 0.050 0.500 0.050 0.050 0.500 0.100 0.200 0.050 0.100 0.050 0.300 0.300 0.300 0.050 0.300 0.100 0.100 0.050 0.050 0.100 0.300 0.100 0.500 0.100 0.500 0.200 0.500 0.100 0.050
4.122 2.639 1.147 0.155 3.409 0.732 1.955 0.206 0.141 2.763 0.109 1.394 0.112 0.077 0.347 0.240 1.661 0.884 0.425 0.644 1.596 1.012 0.029 0.560 2.156 0.182 0.624 2.214 1.036 9.869 10.329 5.568 0.716 1.005 1.049 0.771 0.294 0.427 0.836 0.278 1.435 0.930 1.463 0.992 0.014 0.778 0.149 0.154 0.080 0.172 0.643 1.059 1.447 2.659 0.430 0.509 0.195 0.259 1.800 1.824 2.231 2.209 0.581 0.085 2.536 0.060 0.051 0.833 0.479 0.451
4368.5460 4332.9123 3752.4162 3316.1454 4052.8369 4135.0176 4224.8508 3244.6008 4030.3060 3873.7938 3843.4105 4350.6993 4408.0288 3151.6300 2009.8050 3289.2426 4613.5732 4153.9381 2872.2744 4149.8992 2880.8343 4049.5361 4564.0348 4248.1525 4345.2719 3927.8028 4387.3572 4613.5262 4257.7867 3216.1935 3216.1935 4386.3130 3387.6807 2471.2550 2471.2550 3237.9174 3833.5766 4195.9709 3386.3795 2337.6668 4401.9419 4350.6993 4345.5591 3734.8969 1524.8479 3567.2549 3535.8705 3833.5766 446.6966 4350.6993 3438.5751 4784.6620 4394.4644 4611.7948 3334.6267 3211.0559 4249.5244 4527.9494 4426.0664 4190.2621 2972.8273 2972.8273 4290.7571 4066.1226 4695.8364 4232.1844 3895.5881 4134.7983 5273.6327 3565.4547 (continued on next page)
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S. Yu et al. / Journal of Molecular Spectroscopy 288 (2013) 7–10
Table 2 (continued)
a b
J0K 0a ;K 0c
v 01 v 02 v 03
J 00K 00a ;K 00c
v 001 v 002 v 003
Observed (MHz)
Unc. (MHz)
O:—C: (MHz)
E00 (cm1)
116;6 106;5 66;1 115;6 54;2 22;0 73;5 32;2 21;2 63;3 115;7 41;3 127;6 125;8 123;9 127;5 52;3 62;4 43;1 83;5 105;5 54;2
010 000 020 020 100 020 001 100 020 001 010 020 010 010 000 010 100 020 100 100 010 000
107;3 113;8 54;2 106;5 52;3 21;1 64;2 31;3 10;1 54;2 122;10 40;4 118;3 132;11 132;12 118;4 43;2 53;3 42;2 82;6 96;4 61;5
010 000 001 020 001 020 001 100 020 001 010 020 010 010 000 010 100 020 100 100 010 000
1844542.626 1851205.735 1851949.482 1852505.674 1853189.902 1854654.093 1855827.883 1868780.277 1872985.478 1881404.207 1883966.567 1896998.504 1899124.829 1901609.108 1903496.537 1904324.156 1951083.497 1954235.580 1957473.163 1991297.166 1992747.326 2014864.861
0.100 0.050 0.200 0.200 0.050 0.050 0.100 0.050 0.050 0.100 0.200 0.050 0.100 0.200 0.050 0.200 0.050 0.100 0.050 0.050 0.100 0.050
0.029 0.023 2.121 0.517 0.412 0.196 1.050 0.537 0.075 0.829 0.252 0.102 2.875 0.571 0.019 3.045 2.218 0.158 0.973 3.325 0.127 0.097
3770.7245 1813.2234 4345.2719 5238.3852 4195.9709 3255.3461 4491.3698 3796.5397 3175.4413 4345.2719 3587.6668 3375.2980 4265.9763 3877.0887 2042.3741 4265.9743 4030.8388 3719.4929 3966.5593 4622.9060 3320.9298 542.9058
Laser line. Tentative assignment.
1871701.485(100) GHz. We tried to identify these four transitions by searching the JPL and Cologne databases but did not find a match. They were labelled with ‘‘wrong ID?’’ in the ‘‘MWwaterlines.txt’’ file in the Supplemental Material. In conclusion, in this work, we employed terahertz absorption spectroscopy to study the second triad of water. In the 0.5– 2.0 THz region, 38 pure rotational transitions in (0 3 0), (1 1 0) and (0 1 1) were observed with MW accuracy for the first time. In addition, 91 new transitions in the ground state, (0 1 0) and the first triad (0 2 0), (1 0 0), (0 0 1) were measured with our new multiplier chains covering the 1300–2000 THz region. Acknowledgments We would like to thank Laurent Coudert for providing his linelist of the second triad rotational transitions before his publication. The research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Copyright 2013 California Institute of Technology. Government sponsorship acknoledged. Appendix A. Supplementary material Supplementary data for this article are available on ScienceDirect (www.sciencedirect.com) and as part of the Ohio State University Molecular Spectroscopy Archives (www.library.osu.edu/sites/ msa/jmsa_hp.htm). Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/ 10.1016/j.jms.2013.03.011. References [1] A. Crocker, H.A. Gibbie, M.F. Kimmett, L.E.S. Mathias, Nature 201 (1964) 250– 251. [2] J. Tennyson, P.F. Bernath, L.R. Brown, A. Campargue, A.G. Császár, L. Daumont, R.R. Gamache, J.T. Hodges, O.V. Naumenko, O.L. Polyansky, L.S. Rothman, A.C. Vandaele, N.F. Zobov, A.R. Al Derzi, C. Fábri, A.Z. Fazliev, T. Furtenbacher, I.E. Gordon, L. Lodi, I.I. Mizus, J. Quant. Spectrosc. Radiat. Tansfer 117 (2013) 29– 58. [3] K.M. Menten, A. Lundgren, A. Belloche, S. Thorwirth, M.J. Reid, Astron. Astrophys. 477 (2008) 185–192. [4] S. Yu, J.C. Pearson, B.J. Drouin, M.-A. Martin-Drumel, O. Pirali, M. Vervloet, L.H. Coudert, H.S.P. Müller, S. Brünken, J. Mol. Spectrosc. 279 (2012) 16–25. [5] R.A. Toth, J. Quant. Spectrosc. Radiat. Tansfer 94 (2005) 51–107. [6] S.N. Mikhailenko, W. Le, S. Kassi, A. Campurgue, J. Mol. Spectrosc. 244 (2007) 170–178. [7] L.H. Coudert, G. Wagner, M. Birk, Yu. I. Baranov, W.J. Lafferty, J.-M. Flaud, J. Mol. Spectrosc. 251 (2008) 339–357. [8] L.H. Coudert, private communication. [9] L.H. Coudert, J. Mol. Spectrosc. 154 (1992) 427–442. [10] R. Lanquetin, L.H. Coudert, C. Camy-Peyret, J. Mol. Spectrosc. 206 (2001) 83– 103. [11] L.H. Coudert, O. Pirali, M. Vervloet, R. Lanquetin, C. Camy-Peyret, J. Mol. Spectrosc. 228 (2004) 471–498. [12] L.H. Coudert, G. Wagner, M. Birk, Yu. I. Baranov, W.J. Lafferty, J.-M. Flaud, J. Mol. Spectrosc. 251 (2008) 339–357. [13] B.J. Drouin, F.W. Maiwald, J.C. Pearson, Rev. Sci. Instrum. 76 (2005) 093113. [14] B.J. Drouin, J. Phys. Chem. A, submitted for publication. [15] B.J. Drouin, J.P. Pearson, S. Yu, H. Gupta, IEEE Transactions on Terahertz Science and Technology, 2013, http://dx.doi.org/10.1109/TTHZ.2013.2255915.
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Spectroscopy journal homepage: www.elsevier.com/locate/jms
Note
Terahertz spectroscopy of water in its second triad Shanshan Yu ⇑, John C. Pearson, Brian J. Drouin Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, United States
a r t i c l e
i n f o
Article history: Received 27 February 2013 Available online 9 April 2013 Keywords: High temperature water THz spectroscopy DC discharge
a b s t r a c t Terahertz absorption spectroscopy was employed to measure rotational transitions of water in its second triad 3m2 ; m1 þ m2 and m3 þ m2 . Highly excited water molecules were created with a DC discharge, which allowed observation of transitions with lower state energies up to 5939 cm1. In the 0.5–2.0 THz region, 38 pure rotational transitions in the second triad were observed with MW accuracy for the first time. Additionally, 91 new rotational and ro-vibrational transitions within the ground state, m2 , and the first triad (2m2 ; m1 and m3 ) were measured with multiplier chains covering the 1.3–2.0 THz region. Ó 2013 Elsevier Inc. All rights reserved.
Water provided the first coherent source of THz radiation once its laser action was discovered in 1964 [1]. The general features of the water spectrum have been exceptionally well sorted out after decades of high resolution spectroscopy [2]. However, the extremely non-rigid nature of the water molecule has thus far defied analysis of its Doppler limited frequency measurements to within experimental accuracy. As such, it is still necessary to frequency measure water transitions. The current effort is necessary to support the study of oxygen-rich asymptotic giant branch stars, where water observations have been detected in a number of highly excited vibrational states [3]. Water has three vibrational modes, a symmetric stretch m1 , a bend m2 and an anti-symmetric stretch m3 . We denote these modes as ðv 1 ; v 2 ; v 3 Þ where the commas are omitted for quanta less than 10. The present work follows our previous study [4] in which the rotational and ro-vibrational transitions of water in the ground state, (0 1 0), and the first triad (0 2 0), (1 0 0) and (0 0 1) were measured and analyzed with two different methods. In this study, the pure rotational transitions in the second triad (0 3 0), (1 1 0) and (0 1 1) of water were measured with terahertz absorption spectroscopy for the first time. These three vibrational levels lie high in energy, with vibrational energies of 4667, 5235, 5331 cm1, respectively. In addition, 91 new transitions in the ground state, (0 1 0), and the first triad (0 2 0), (1 0 0) and (0 0 1) were measured with our new multiplier chains covering the 1300–2000 THz region. Since the previous paper [4] provided a detailed analysis and the present data for the lowest five states is consistent with residuals from the previous work, no additional fitting of line positions was performed. The new data in the second triad are too limited to have a significant impact on molecular constants. As a result, no data analysis, i.e., fit of the measured line positions to ⇑ Corresponding author. E-mail address: [email protected] (S. Yu). 0022-2852/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jms.2013.03.011
Hamiltonian models, was carried out and only the measured line positions are reported for the benefit of velocity resolved astronomical spectroscopy. There is a vast literature dealing with experimental investigations of the second triad of water and we refer readers to the latest four papers [2,5–7] for details on previous studies. The obtained maximum J was 18 in Toth [5], 17 in Mikhailenko et al. [6], 18 in Coudert et al. [7]. To guide our experimental search for the line positions of pure rotation transitions in the second triad, we used the predictions from a global analysis by Coudert [8], which is based on the Bending-Rotation approach [9–12] and is still in progress. The frequency multiplied submillimeter spectrometer (FMSS) used for the measurements is described in Ref. [13], with eight multiplier chains covering the 290–1230 and 1575–1626 GHz ranges with some small gaps in between. The present work involves four new multiplier chains covering the 1300–2000 GHz region [14,15]. The measurements were carried out with a 1.2-m-long DC discharge cell and with water pressures ranging from 100 mtorr to 180 mtorr. Typical discharge currents were 350 mA and the voltage across the electrodes was about 3 kV. Note that our frequency positions were not corrected for pressure shifts. The uncertainties were estimated to be between 50 and 500 kHz. Fig. 1 shows the observed J 0K 0a ;K 0c J 00K 00a ;K 00c ¼ 63;3 62;4 rotational line in the (0 1 1) vibrational state. A few H2O2 transitions were also observed while we searched around the predicted H2O transition frequencies. Table 1 lists the assignment, observed position, experimental uncertainty, difference from the Bending-Rotation model in Ref. [8], and lower state energy for the newly measured 38 pure rotational transitions of water in the second triad (0 3 0), (1 1 0) and (0 1 1). The model results differ from the observed frequencies from 19 MHz to 14 MHz. The observed JðMaxÞ was 6 and the observed highest energy level was at 5939 cm1. We have searched but
8
S. Yu et al. / Journal of Molecular Spectroscopy 288 (2013) 7–10
(011) 63, 3 − 62, 4
1887270
1887290
1887310
1887330
1887350
188737 0
Frequency (MHz) Fig. 1. The observed ðv 1 v 2 v 3 Þ ¼ ð0 1 1Þ, J0K 0a ;K 0c J00K 00a ;K 00c ¼ 63;3 62;4 pure rotational water line together with severe baseline. The lower state energy of this transition is 5939 cm1. The integration time was 1.5 s on each point. An experimental uncertainty of 100 kHz was assigned to the measured line position.
failed to observe transitions with larger J, which has led us to believe that in Fig. 1 of our previous study [4] the tentative assignment of the 1151447 MHz line to J ¼ 12 of (0 3 0)–(1 1 0) is in question. The DC discharge only modestly enhances the rotational
temperature, while it provides a significant enhancement of the vibrational temperature. The result is that only the lowest rotational levels in excited vibrational states are sufficiently populated to observe. These new measurements were added to the compiled list of microwave water transitions given in our previous work [4] and the updated list is given in the ‘‘MWwaterlines.txt’’ file in the Supplemental Material of this note. Table 2 lists the assignment, observed position, experimental uncertainty, difference from the Bending-Rotation model in Ref. [4], and lower state energy for the newly measured 91 rotational and ro-vibrational transitions of water in the ground state, m2 ¼ 1 and the first triad (0 2 0), (1 0 0), (0 0 1). Differences up to 10 MHz were found between the model results and the observed frequencies. Laser action was observed at 532 644 GHz and 1 312 041 GHz. These new measurements were also added to the ‘‘MWwaterlines.txt’’ file in the Supplemental Material of this note. To validate existing datasets, 52 previously measured transitions in the five lowest states were also re-measured. These re-measured frequencies were also included in the ‘‘MWwaterlines.txt’’ file in the Supplemental Material. We re-assessed experimental uncertainties for previously reported frequencies based on repeated measurements. All the remeasured positions agree well with previous values, except for the 105;6 —96;3 and 106;5 —107;4 lines of the (0 1 0) state. These two lines were measured previusly by the Cologne group in our previous work [4]. The JPL-measured vs. Cologne-measured values for these two lines are 1866271.866(50) vs. 1866269.960(300) and 1871695.115(50) vs.
Table 1 Assignment, observed position, experimental uncertainty, difference from the Bending-Rotation model in Ref. [8], and lower state energy for the newly measured 38 pure rotational transitions of water in the second triad (0 3 0), (1 1 0) and (0 1 1). J0K 0a ;K 0c
v 01 v 02 v 03
J00K 00a ;K 00c
v 001 v 002 v 003
Observed (MHz)
Unc. (MHz)
O:—C: (MHz)
E00 (cm1)
11;1 11;1 11;1 11;0 11;0 11;0 21;2 21;2 20;2 20;2 21;1 21;1 21;1 22;0 22;0 22;1 22;1 30;3 30;3 30;3 31;2 31;2 31;2 32;1 22;0 41;3 41;3 41;3 41;3 41;3 42;2 42;2 32;1 52;3 52;3 62;4 62;4 63;3
030 110 011 030 110 011 110 011 110 011 030 110 011 110 011 110 011 030 110 011 030 110 011 110 030 030 110 011 110 011 110 011 030 110 011 110 011 011
00;0 00;0 00;0 10;1 10;1 10;1 10;1 10;1 11;1 11;1 20;2 20;2 20;2 21;1 21;1 21;2 21;2 21;2 21;2 21;2 30;3 30;3 30;3 31;2 31;3 32;2 32;2 32;2 40;4 40;4 41;3 41;3 41;4 51;4 51;4 61;5 61;5 62;4
030 110 011 030 110 011 110 011 110 011 030 110 011 110 011 110 011 030 110 011 030 110 011 110 030 030 110 011 110 011 110 011 030 110 011 110 011 011
1519493.285 1174679.308 1154046.217 988270.194 637714.013 614348.435 1711840.578 1695031.030 894833.079 928596.443 1199093.531 839546.907 822484.021 1436857.865 1363583.637 1896020.257 1826929.314 1375728.372 1624633.034 1655545.358 1559052.800 1194827.872 1189488.320 1350535.743 1062841.460 1044018.072 1855413.208 1919778.551 1719294.989 1727231.121 1406976.895 1341289.223 873631.048 1560690.153 1543549.888 1923327.454 1936356.238 1887327.909
0.100 0.300 0.100 0.100 0.200 0.200 0.100 0.200 0.300 0.300 0.200 0.100 0.100 0.300 0.200 0.200 0.300 0.200 0.200 0.300 0.100 0.100 0.100 0.100 0.300 0.200 0.300 0.100 0.200 0.100 0.300 0.100 0.300 0.100 0.200 0.100 0.200 0.100
3.045 2.876 2.475 3.856 3.063 2.193 3.211 3.279 9.241 6.304 2.201 0.038 0.036 8.203 5.131 2.430 0.010 19.458 8.769 6.399 0.410 4.288 3.385 7.251 18.554 10.881 13.340 5.192 6.915 6.736 0.281 4.045 11.691 0.112 5.927 0.069 8.240 7.095
4666.7892 5234.9750 5331.2671 4690.5797 5258.3994 5354.8709 5258.3994 5354.8709 5274.1582 5369.7619 4737.2026 5304.0063 5400.7367 5332.0105 5428.1719 5315.5003 5411.4109 4759.0232 5315.5003 5411.4109 4804.9133 5369.6920 5466.6342 5409.5470 4820.7622 4926.8619 5449.0299 5544.2486 5453.5701 5550.6713 5510.9194 5608.2857 4902.1302 5634.1209 5731.9161 5776.7913 5874.7467 5939.3363
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Table 2 Assignment, observed position, experimental uncertainty, difference from the Bending-Rotation model in Ref. [4], and lower state energy for the newly measured 91 rotational and ro-vibrational transitions of water in the ground state, m2 ¼ 1 and the first triad (0 2 0), (1 0 0), (0 0 1). J0K 0a ;K 0c 84;4 62;4 107;3 31;2 82;7 53;2 53;3 147;8 42;3 72;6 133;11 64;3 72;6 11;1 107;3 31;2 74;4 62;5 145;10 52;3 137;7 52;3 94;5 62;5 64;3 41;4 93;7 74;3 63;3 1210;2 1210;3 93;7 41;3 118;4 118;3 30;3 22;1 53;2 113;8 72;5 73;5 66;1 64;2 30;3 104;7 164;12 123;10 30;3 53;3 63;3 42;2 104;7 72;6 103;8 32;1 155;11 63;3 73;4 73;4 62;4 129;4 129;3 62;4 43;1 84;5 63;4 32;2 52;3 105;6 52;3
v 01 v 02 v 03 020 001 010 020 020 100 001 000 001 020 010 100 001 020 000 020 001 100 000 001 000 100 020 001 100 001 020 001 100 000 000 020 020 000 000 020 001 001 010 010 100 020 100 100 000 000 010 001 000 001 020 020 001 020 020 000 100 001 100 100 000 000 001 001 100 100 001 001 100 020
J 00K 00a ;K 00c 75;3 71;7 98;2 22;1 73;4 44;1 44;0 154;11 33;0 63;3 124;8 62;4 63;3 00;0 98;2 30;3 65;1 53;2 152;13 51;4 144;10 51;4 85;4 53;2 54;2 41;3 80;8 65;2 54;2 1111;1 1111;0 84;4 32;2 109;1 109;2 21;2 21;2 52;3 122;11 81;8 64;2 62;4 54;1 21;2 111;10 173;15 114;7 21;2 60;6 62;4 41;3 95;4 64;3 94;5 31;2 162;14 62;4 72;5 72;5 61;5 1110;1 1110;2 61;5 42;2 75;2 70;7 31;3 44;0 103;7 51;4
v 001 v 002 v 003 020 001 010 020 020 100 001 000 001 020 010 001 001 020 000 020 001 100 000 001 000 100 020 001 001 100 100 001 100 000 000 020 020 000 000 020 001 001 010 010 100 001 001 100 000 000 010 001 000 001 020 020 100 020 020 000 100 001 100 100 000 000 001 001 100 100 001 100 001 020
Observed (MHz) a
532644.463 533240.158 548868.742 554055.105 566500.881 567221.559 583211.504 591693.639 591977.103 610798.188 1088558.746 1312041.828a 1328798.943 1332979.607 1335984.742 1360579.357 1361104.994 1362642.145 1378163.986 1381195.839 1386269.187 1390554.341 1431808.865 1451322.977 1474751.265 1482735.850 1486471.369 1487702.793 1511691.386 1516088.633b 1516088.633b 1517769.992 1525774.148 1529130.871 1529245.865 1538690.835 1563748.988 1564363.252 1638667.804 1646633.295 1675143.165 1689240.474 1690312.124 1693083.943 1693470.368 1694135.960 1695430.101 1716391.671 1716956.789 1718695.008 1719735.763 1722884.590 1735452.117 1737030.079 1742476.965 1753305.893 1759388.834 1760795.953 1766550.041 1776637.616 1794630.094 1794648.504 1797024.539 1808972.444 1815476.292 1820502.441 1831064.289 1833907.958 1839396.686 1842750.067
Unc. (MHz)
O:—C: (MHz)
E00 (cm1)
0.050 1.000 0.200 0.200 0.100 0.100 0.100 0.200 0.200 0.500 0.200 0.100 0.200 0.050 0.050 0.050 0.200 0.100 0.050 0.050 0.300 0.050 0.300 0.500 0.500 0.500 0.300 0.500 0.300 0.200 0.200 0.200 0.100 0.050 0.100 0.050 0.050 0.050 0.500 0.100 0.200 0.050 0.500 0.050 0.050 0.500 0.100 0.200 0.050 0.100 0.050 0.300 0.300 0.300 0.050 0.300 0.100 0.100 0.050 0.050 0.100 0.300 0.100 0.500 0.100 0.500 0.200 0.500 0.100 0.050
4.122 2.639 1.147 0.155 3.409 0.732 1.955 0.206 0.141 2.763 0.109 1.394 0.112 0.077 0.347 0.240 1.661 0.884 0.425 0.644 1.596 1.012 0.029 0.560 2.156 0.182 0.624 2.214 1.036 9.869 10.329 5.568 0.716 1.005 1.049 0.771 0.294 0.427 0.836 0.278 1.435 0.930 1.463 0.992 0.014 0.778 0.149 0.154 0.080 0.172 0.643 1.059 1.447 2.659 0.430 0.509 0.195 0.259 1.800 1.824 2.231 2.209 0.581 0.085 2.536 0.060 0.051 0.833 0.479 0.451
4368.5460 4332.9123 3752.4162 3316.1454 4052.8369 4135.0176 4224.8508 3244.6008 4030.3060 3873.7938 3843.4105 4350.6993 4408.0288 3151.6300 2009.8050 3289.2426 4613.5732 4153.9381 2872.2744 4149.8992 2880.8343 4049.5361 4564.0348 4248.1525 4345.2719 3927.8028 4387.3572 4613.5262 4257.7867 3216.1935 3216.1935 4386.3130 3387.6807 2471.2550 2471.2550 3237.9174 3833.5766 4195.9709 3386.3795 2337.6668 4401.9419 4350.6993 4345.5591 3734.8969 1524.8479 3567.2549 3535.8705 3833.5766 446.6966 4350.6993 3438.5751 4784.6620 4394.4644 4611.7948 3334.6267 3211.0559 4249.5244 4527.9494 4426.0664 4190.2621 2972.8273 2972.8273 4290.7571 4066.1226 4695.8364 4232.1844 3895.5881 4134.7983 5273.6327 3565.4547 (continued on next page)
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S. Yu et al. / Journal of Molecular Spectroscopy 288 (2013) 7–10
Table 2 (continued)
a b
J0K 0a ;K 0c
v 01 v 02 v 03
J 00K 00a ;K 00c
v 001 v 002 v 003
Observed (MHz)
Unc. (MHz)
O:—C: (MHz)
E00 (cm1)
116;6 106;5 66;1 115;6 54;2 22;0 73;5 32;2 21;2 63;3 115;7 41;3 127;6 125;8 123;9 127;5 52;3 62;4 43;1 83;5 105;5 54;2
010 000 020 020 100 020 001 100 020 001 010 020 010 010 000 010 100 020 100 100 010 000
107;3 113;8 54;2 106;5 52;3 21;1 64;2 31;3 10;1 54;2 122;10 40;4 118;3 132;11 132;12 118;4 43;2 53;3 42;2 82;6 96;4 61;5
010 000 001 020 001 020 001 100 020 001 010 020 010 010 000 010 100 020 100 100 010 000
1844542.626 1851205.735 1851949.482 1852505.674 1853189.902 1854654.093 1855827.883 1868780.277 1872985.478 1881404.207 1883966.567 1896998.504 1899124.829 1901609.108 1903496.537 1904324.156 1951083.497 1954235.580 1957473.163 1991297.166 1992747.326 2014864.861
0.100 0.050 0.200 0.200 0.050 0.050 0.100 0.050 0.050 0.100 0.200 0.050 0.100 0.200 0.050 0.200 0.050 0.100 0.050 0.050 0.100 0.050
0.029 0.023 2.121 0.517 0.412 0.196 1.050 0.537 0.075 0.829 0.252 0.102 2.875 0.571 0.019 3.045 2.218 0.158 0.973 3.325 0.127 0.097
3770.7245 1813.2234 4345.2719 5238.3852 4195.9709 3255.3461 4491.3698 3796.5397 3175.4413 4345.2719 3587.6668 3375.2980 4265.9763 3877.0887 2042.3741 4265.9743 4030.8388 3719.4929 3966.5593 4622.9060 3320.9298 542.9058
Laser line. Tentative assignment.
1871701.485(100) GHz. We tried to identify these four transitions by searching the JPL and Cologne databases but did not find a match. They were labelled with ‘‘wrong ID?’’ in the ‘‘MWwaterlines.txt’’ file in the Supplemental Material. In conclusion, in this work, we employed terahertz absorption spectroscopy to study the second triad of water. In the 0.5– 2.0 THz region, 38 pure rotational transitions in (0 3 0), (1 1 0) and (0 1 1) were observed with MW accuracy for the first time. In addition, 91 new transitions in the ground state, (0 1 0) and the first triad (0 2 0), (1 0 0), (0 0 1) were measured with our new multiplier chains covering the 1300–2000 THz region. Acknowledgments We would like to thank Laurent Coudert for providing his linelist of the second triad rotational transitions before his publication. The research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Copyright 2013 California Institute of Technology. Government sponsorship acknoledged. Appendix A. Supplementary material Supplementary data for this article are available on ScienceDirect (www.sciencedirect.com) and as part of the Ohio State University Molecular Spectroscopy Archives (www.library.osu.edu/sites/ msa/jmsa_hp.htm). Supplementary data associated with this
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