Highly sensitive absorption spectroscopy of carbon dioxide by ICLAS-VeCSEL between 8800 and 9530cm−1

Please download to get full document.

View again

of 7
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Categories
Published
ABSTRACT The absorption spectrum of carbon dioxide has been studied between 8800 and 9530 cm−1 by intracavity laser absorption spectroscopy based on a vertical external cavity surface emitting lasers (VeCSEL). Previous laboratory spectra at high
  Highly sensitive absorption spectroscopy of carbon dioxideby ICLAS-VeCSEL between 8800 and 9530 cm  1 Y. Ding  a , A. Campargue  a,* , E. Bertseva  a , S. Tashkun  b , V.I. Perevalov  b a Laboratoire de Spectrome´ trie Physique (CNRS, UMR 5588), Universite´  Joseph Fourier de Grenoble, B.P. 87 38402 Saint-Martin-d   He` res Cedex, France b Laboratory of Theoretical Spectroscopy, Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences,1, Akademicheskii av., 634055 Tomsk, Russia Received 10 November 2004; in revised form 20 December 2004Available online 16 February 2005 Abstract The absorption spectrum of carbon dioxide has been studied between 8800 and 9530 cm  1 by intracavity laser absorption spec-troscopy based on a vertical external cavity surface emitting lasers (VeCSEL). Previous laboratory spectra at high resolution werenearly absent in the considered spectral region. Experiments were carried with natural carbon dioxide and with  13 C enriched carbondioxide leading to the determination of the rovibrational parameters of a total of 15 very weak vibrational transitions, including twobands of the  16 O 13 C 18 O isotopologue. The observed transitions are assigned to components of the 2 m 1  + 3 m 3  triad and of the muchweaker 5 m 1  +  m 3  hexad. Our measured line positions are found in excellent agreement with the predictions of the effective Hamilto-nians developed for  12 C 16 O 2  and  13 C 16 O 2  but significant deviations were evidenced for the  16 O 13 C 18 O minor isotopologue. The rel-ative band intensities within each polyad are also discussed on the basis of the effective Hamiltonian model.   2005 Elsevier Inc. All rights reserved. Keywords:  Carbon dioxide;  12 C 16 O 2 ;  13 C 16 O 2 ; Intracavity laser absorption spectroscopy; VCSEL; ICLAS; Rovibrational Hamiltonian 1. Introduction This contribution is a continuation of our effortsaimed at investigating the high overtone absorptionspectrum of carbon dioxide by intracavity laser absorp-tion spectroscopy (ICLAS). Fig. 1 presents a review of the observed [1–6] and predicted [7,8] levels above 8400 cm  1 . For symmetry reasons, the transitions ob-served by absorption from the ground state correspondto an odd quantum number of the antisymmetricstretch,  m 3 . Due to the vibrational resonance betweenthe  m 1  stretching and  m 2  bending modes, the( V  1 , V  2 , l  2 , V  3 ) states with the same value of ( V  1  + 2 V  2 )are coupled leading to a polyad structure. In the HI-TRAN notation, the ( V  1  + 1) eigenstates are labelled V    Max1  ; V    2  ¼ l 2 ; l 2 ; V    3 ; i 1 6 i 6 ð V    1 þ 1 Þ , where  V    Max1  is the maxi-mum value of the quantum number associated withthe  m 1  symmetric stretching mode and  i   is a rankingnumber decreasing with the energy. As the  m 3  normalmode brings most of the oscillator strength, polyads cor-responding to the higher  V  3  quantum number have ahigher relative intensity.Recently, the vertical external cavity surface emittinglasers (VeCSEL) were adapted for ICLAS experimentsallowing for highly sensitive absorption spectroscopyinvestigations in the near infrared [9,10]. In a first contri-bution [6], we reported the observation of two compo-nents of the [(20 0 3), (12 0 3), (04 0 3)] triad of   12 C 16 O 2 ,namely 20031 and 20032 in HITRAN notation [11], atabout 9631 and 9517 cm  1 , respectively. In the present 0022-2852/$ - see front matter    2005 Elsevier Inc. All rights reserved.doi:10.1016/j.jms.2004.12.008 * Corresponding author. Fax: +33 4 76 63 54 95. E-mail address:  Alain.Campargue@ujf-grenoble.fr (A. Campar-gue). www.elsevier.com/locate/jms Journal of Molecular Spectroscopy 231 (2005) 117–123  work,theuseofdifferentVeCSELhasgivenaccesstothe8800–9530 cm  1 region where the 20033–00001 and20032–00001 bands could be detected together with theassociated hot bands and three components of the muchweaker 5 m 1  +  m 3  hexad. Similar experiments were carriedwith a sampleof  13 CO 2 ,allowingfor thefirst detectionof the 50013–00001 transition and the observation of the2 m 1  + 3 m 3  triad of   13 C 16 O 2 . In the spectra recorded with 13 C enriched carbon dioxide, we could furthermore iden-tify the 20031–00001 and 20032–00001 bands of the 16 O 13 C 18 O isotopologue. Altogether, fifteen bands wererotationally analyzed, four of which are newly reported,the analysis of the others being improved.The review of the previous studies [12–18] relative tothe 2 m 1  + 3 m 3  triad of   12 C 16 O 2  was discussed in [6]. Mostof the spectroscopic information available in the consid-ered spectral region was obtained from the high resolu-tion Fourier Transform spectra of Venus atmosphererecorded by Connes and Michel [15] and analyzed byMandin [16] about 30 years ago. In absence of labora-tory investigation with equivalent or better sensitivity,these Venus data were largely used in the HITRANdatabase [11] in particular in the higher energy regionwhere the bands are extremely weak. But these spectrasuffered from the experimental conditions of the record-ings (high pressure, translational Do¨ppler effects, andline overlapping) which limited the accuracy of the re-trieved line wavenumbers. The need of laboratory inves-tigations was underlined by several authors, inparticular by Goldman and co-workers [19] whorecently evidenced inconsistencies in the HITRANdatabase when they analysed the high resolution solaratmospheric spectrum around 1  l m [19]. The results of  our previous ICLAS-VeCSEL study relative to the2 m 1  + 3 m 3  triad of   12 C 16 O 2  [6] improved the consistencyof their analysis and were very recently included in the2004 version of the HITRAN database [32].For completeness, we mention the previous labora-tory investigations at high spectral resolution due toPoplavskii et al. [17] and Sinitsa [18]. These authors used ICLAS based on a neodymium glass around 9400 cm  1 to rotationally analyse components of the 2 m 1  + 3 m 3 triad of several isotopologues but their analysis sufferedof limited wavenumber accuracy. 2. Experimental The spectra were recorded with the same experimen-tal setup based on a VeCSEL, previously described in[9,10] and applied to the spectroscopy of N 2 O [20–22],H 2 S [23], and H 2 O [24] for instance. By taking advan-tage of the non-uniformity of the layers constitutingthe VCSEL, the newly used structure allows for a con-tinuous tuning of the laser in the 8800–9620 cm  1 spec-tral region, simply by translating the VCSEL mountedon a translation stage.The typical pressure was 100 hPa and the spectrawere recorded with generation times up to 120  l s, lead-ing to equivalent absorption path lengths of the order of 20 km. The present sensitivity is of the order of  a min  5  ·  10  9 cm  1 i.e., not as good as that we could Fig. 1. Overview of the ( l  2  = 0) energy levels of   12 C 16 O 2  and  13 C 16 O 2  observed (or observable) by absorption above 8400 cm  1 . The experimentalvalues with the relevant reference are given when available: camp94, Ref. [1]; camp99, Ref. [2]; weir99, Ref. [3]; tash00, Ref. [4]; weir01, Ref. [5]; ding02, Ref. [6]; ding05, this work; bailly81, Ref. [28]; bailly84, Ref. [29]. Otherwise, the energy values indicated in italics are those predicted by using the effective Hamiltonian models developed in [7] and [8] for  12 C 16 O 2  and  13 C 16 O 2 , respectively. Note that Bailly et al. [28] observed the 00051 level of  12 C 16 O 2  and  13 C 16 O 2  [29] in the FTIR emission spectra of carbon dioxide excited by a dc discharge.118  Y. Ding et al. / Journal of Molecular Spectroscopy 231 (2005) 117–123  achieve with other VCSEL samples at higher energy[10,20–24]. This is due to the fact that the present samplewas obtained from the edge of an epytaxy wafer, wherethe accuracy of the layer growth is not optimum leadingto limited lasing characteristics, but at the same time,allowing for higher wavelength tunability.The accurate calibration of the ICLAS spectrum re-quires the knowledge of at least two reference line posi-tions for each 10 cm  1 wide section. For this purpose,water and carbon dioxide were successively injected inthe intracavity cell and their respective spectra were re-corded within a few tens seconds. Below 9200 cm  1 ,the water line position given in the HITRAN database[11] were adopted while above 9250 cm  1 , we used theH 2 O wavenumbers provided in [25]. To check the con-sistency of the calibration, some additional experimentswere carried by adding a very low concentration of acet-ylene into the CO 2  sample and using C 2 H 2  line positionsmeasured by Fourier transform spectroscopy with a lineposition accuracy around 10  3 cm  1 [33]. Depending onthe bandstrength and on the quality of the referencelines, our wavenumber uncertainty is estimated to rangebetween 2  ·  10  3 and 5  ·  10  3 cm  1 . As reflected belowby the  rms  value of the fit achieved in the rovibrationalanalysis, the uncertainty is larger for the 5001 i   compo-nents of the 626 isotopologue as the signal-to-noise ratioof the spectra was limited both by the very weak band-strength of the considered bands and their superpositionwith relatively intense atmospheric water lines.The ICLAS-VeCSEL spectrum in the region of thebandhead of the 21132–01101 hot band of   12 C 16 O 2  isdisplayed in Fig. 2 while Fig. 3 shows the  R  branch of the 20032–00001 transition of   13 C 16 O 2  superimposedto the 20031–00001 band of   16 O 13 C 18 O. The stated iso-topic concentration of   13 C carbon atom in the  13 C en-riched sample (Aldrich Chemical) is 99% and less than3% of   18 O for oxygen atom. A mass spectroscopy exper-iment previously performed with a similar sample [8] hasshowed an  18 O enrichment value of 1.2% (then 2.4% forthe 638 isotopologue) in agreement with the observedrelative intensities of the 636 and 638 bands (see Fig. 3). 3. Results A summary of the observations relative to the5 m 1  +  m 3  hexad and the 2 m 1  + 3 m 3  triad is presented in Ta-ble 1 for the 626, 636, and 638 isotopologues. Comparedto previous Venus data [16], the new observations con-cern only the 636 and 638 isotopologues. However, thecomparison with the wavenumber values obtained byMandin confirms that around 9500 cm  1 Venus dataare systematically overestimated by about 0.01 cm  1 [6]. This shift has the tendency to decrease with thewavenumber down to 0.003–0.004 cm  1 in the regionaround 6000–6800 cm  1 [7,8].The following expression was used for the vibration– rotational energy levels of the upper and lower states T  v  ¼ G  v ð v 1 ; v l 2 2  ; v 3 Þþ  F   v ð  J  Þ ;  ð 1 Þ where  G  v  and  F  v  are the vibrational and rotational con-tributions, respectively, with  F   v ð  J  Þ¼  B v  J  ð  J   þ 1 Þ  D v  J  2 ð  J   þ 1 Þ 2 ;  ð 2 Þ In the fitting procedure, the rotational constants of theground state were constrained to their literature values[26] and the quantities  D G  v ,  D B  v , and  D D v  were fitted(note that according to the above expressions, the bandsrcin  v 0  coincides with  D G  v ). In the case of the hot Fig. 2. ICLAS-VeCSEL spectrum of   12 C 16 O 2  in the region of thebandhead of the 21132–01101 hot band of   12 C 16 O 2 . The strong linescorrespond to the  P  (34)–  P  (20) transitions of the 20032–00001 bandcentered at 9516.958 cm  1 . The spectrum was recorded at a pressure of about 118 hPa (90 Torr) with an equivalent absorption path length of the order of 13 km.Fig. 3. Part of the  R  branch of the 20032–00001 band of   13 C 16 O 2 recorded by ICLAS-VeCSEL ( P   = 137 hPa (104 Torr),  l  eq  15 km).The weaker  R  branch of the 20031–00001 band of   16 O 13 C 18 O is alsoobserved in this spectral region. Y. Ding et al. / Journal of Molecular Spectroscopy 231 (2005) 117–123  119  bands, the  ee  and  ff   sub bands were fitted independently.The retrieved spectroscopic parameters are listed inTables 2–4 for the 626, 636, and 638 isotopologues,respectively. The values of the  rms  of the fit ranging be-tween 2  ·  10  3 and 5  ·  10  3 cm  1 are mainly limited bythe experimental uncertainty indicating that no signifi-cant perturbation affects the considered bands. The listof assigned rotational lines is attached to the paper asSupplementary Material.The comparison with Mandin  s results included inthese Tables, shows an overall good agreement exceptfor the band srcins which differ by about 10  2 cm  1 .However, the increased number of transitions observedby ICLAS leads generally to a better determination of the parameters, in particular of the centrifugal distortionconstant.It is interesting to compare our observations with thepredictions of the effective Hamiltonians developed for Table 1Comparison of the observed vibrational term values of the 5 m 1  +  m 3  hexad and of the 2 m 1  + 3 m 3  triad with the predictions of the respective effectiveHamiltonian models for the 626 [7], 636 [8], and 638 [27] isotopologues of carbon dioxide 626 636 638Obs. Calc. Obs. Calc. Obs. Calc.50016 8480.242 8322.048 8206.70350015 8676.716 a 8676.711 8529.688 8398.76150014 8831.481 8831.474 8703.404 8552.906 * 50013 8965.217 8965.220 8835.571 8835.570 8677.73350012 9137.795 9137.790 8970.077 8832.53350011 9349.841 9145.089 * 9026.50220033 9388.983 9388.981 9158.876 9158.880 * 9071.72120032 9516.958 9516.957 9302.138 9302.139 9198.193 9198.13720031 9631.341 b 9631.341 9404.128 9404.130 9302.995 9302.983Three bands marked with a star are predicted to be perturbed. a From Mandin [16]. b ICLAS-VeCSEL [6].Table 2Spectroscopic parameters (in cm  1 ) of the rovibrational bands of   12 C 16 O 2  recorded by ICLAS-VeCSEL between 8805 and 9530 cm  112 C 16 O 2  G  v  D G  v b B  v  D v  ·  10 7 J  max P/Rn / N  c rms  ·  10 3 00001 a 0.0 0.39021899 1.3333801101 e a 667.37996 0.39063900 1.3529501101  f  a 667.37996 0.39125465 1.3608850014–00001  8831.4805  8831.4805 (19) 0.3851278 (72) 0.860 (47) 18/38 21/22 3.9 8831.482 (10) 0.3851466 (41) 0.954 (27) 44/38 2.9 50013–00001 8965.2168 8965.2168 (20) 0.3858989 (58) 0.7137 (34) 38/44 32/34 5.2 8965.2247 (5) 0.3859242 (17) 0.746 (10) 38/40 1.2 50012–00001 9137.7949 9137.7949 (35) 0.387753 (18) 0.371 (19) 14/28 10/12 3.5 9137.7993 (11) 0.3877875 (61) 0.650 (65) 28/30 2.3 21133 e  –01101 e  9987.36536 9319.9854 (27) 0.382408 (13) 1.69 (11) 33/33 23/27 4.5 9320.0089 (29) 0.382291 (26)   0.065 (4) 3.4 21133  f   –01101  f   9987.36826 9319.9883 (23) 0.391255 (12) 1.68 (12) 34/28 21/25 3.9 9319.9964 (53) 0.383611 (33) 1.84 (36) 6.9 20033–00001 9388.98340 9388.98340 (72) 0.3823801 (17) 1.8088 (37) 52/48 49/52 2.7 9388.9937 (4) 0.38238062 (25) 1.851 (35) 44/46 1.2 21132 e  –01101 e  10145.4874 9478.1074 (11) 0.3808631 (44)   0.251(38) 41/37 30/35 3.0 9478.1246 (15) 0.3808557 (60)   0.286 (44) 4.2 21132  f   –01101  f   10145.4998 9478.11984 (77) 0.3821750 (25) 1.115 (15) 44/44 35/40 2.4 9478.1330 (11) 0.3821671 (51) 1.087 (44) 2.7  20032–00001 9516.95800 9516.95800 (58) 0.38049100 (92) 1.3648 (25) 62/64 61/65 2.4 9516.9690 (11) 0.3804955 (24) 1.389 (10) 54/56 4.1Notes.  The uncertainties are given in parenthesis in the unit of the last quoted digit. The parameters listed in italics are the results of Mandin [16]. a The parameters of the lower levels are taken from [26]. b Band srcin. c n , number of transitions included in the fit;  N  , number of assigned rotational transitions.120  Y. Ding et al. / Journal of Molecular Spectroscopy 231 (2005) 117–123  the three considered isotopologues  12 C 16 O 2  [7]  13 C 16 O 2 [8], and  16 O 13 C 18 O [27] as the sets of rovibrationalparameters were recently refined. The comparison of the vibrational term values included in Table 1 showsan agreement close to the experimental uncertainty forthe 626 and 636 isotopologues while a deviation of 5.6  ·  10  2 cm  1 , is noted for the 20032 level of the 638minor isotopologue. The rotational structure of the20033 level of   13 C 16 O 2  is predicted [8] to be perturbedat  J   around 51 by a third order anharmonic resonanceinteraction of the type ( D V  1  = 3,  D V  3  =  2) with the50011 level. However, as these high  J   transitions werenot observed, the corresponding band was consideredisolated in the fit of the rovibrational parameters.A more detailed comparison of the measured linepositions to those of Venus spectrum [16] and computedon the basis of the effective Hamiltonin models [7,8] ispresented on Figs. 4 and 5 for the  12 C 16 O 2  and 13 C 16 O 2  isotopologues respectively. These figures clearlyshow the systematic shift of Venus data. Table 3Spectroscopic parameters (in cm  1 ) of the rovibrational bands of   13 C 16 O 2  recorded by ICLAS-VeCSEL between 8805 and 9430 cm  113 C 16 O 2  G  v  D G  v b B  v  D v  ·  10 7 J  max P  / Rn/N  c rms  ·  10 3 00001 a 0.0 0.39023754 1.3334601101 e a 648.47803 0.39061133 1.3548901101  f   a 648.47803 0.39124542 1.3637750013–00001 8835.5714 8835.5714 (19) 0.3849309 (99) 1.237 (83) 22/38 21/25 4.620033–00001 9158.87606 9158.87606 (89) 0.3831969 (31) 1.685 (19) 42/42 38/42 2.921132 e  –01101 e  9910.8067 9262.3286 (10) 0.3813553 (36) 0.401 (22) 33/41 32/35 3.121132  f   –01101  f   9910.8072 9262.32919 (96) 0.3826333 (37) 1.208 (26) 34/42 31/35 2.720032–00001 9302.13825 9302.13825 (74) 0.3811492 (19) 1.4996 (89) 50/40 45/46 2.7 9302.1446 (10) 0.3811439 (70) 1.405 (92) 2.1 20031–00001 9404.12812 9404.12812 (67) 0.3806759 (14) 0.9969 (52) 56/38 47/48 2.6 9404.1394 (16) 0.380642 (14) 0.64 (24) 2.6  21131 e  –01101 e  10050.5373 9402.0593 (16) 0.3809897 (96)   0.043 (108) 31/29 20/24 3.121131  f   –01101  f   10050.5218 9402.0438 (26) 0.381992 (11) 1.22 (10) 34/24 20/23 4.3 Notes.  The uncertainties are given in parenthesis in the unit of the last quoted digit. The parameters listed in italics are the results of Mandin [16]. a The parameters of the lower levels are taken from [26]. b Band srcin. c n , number of transitions included in the fit;  N  , number of assigned rotational transitions.Table 4Spectroscopic parameters (in cm  1 ) of the 20031–00001 and 20032–00001 transitions of   16 O 13 C 18 O 16 O 13 C 18 O  G  v  B  v  D v  ·  10 7 J  max P  / Rn / N  b rms  ·  10 3 00001 a 0.0 0.36818450 1.1870120032–00001 9198.19309 (69) 0.3593945 (26) 1.234 (18) 41/38 73/78 3.020031–00001 9302.9949 (12) 0.3598245 (75) 0.928 (82) 32/28 41/45 4.0 Notes.  The uncertainties are given in parenthesis in the unit of the last quoted digit. a The parameters for the ground level are taken from [26]. b n , number of transitions included in the fit;  N  , number of assigned rotational transitions.Fig. 4. Comparison of the individual line positions of   12 C 16 O 2  to thosemeasured in the Venus spectrum [16] and to those predicted with thehelp of the effective Hamiltonian model [7]. The lines overlapped by atmospheric water lines or other CO 2  lines are not included in the plot. Y. Ding et al. / Journal of Molecular Spectroscopy 231 (2005) 117–123  121
Similar documents
View more...
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks