Supersonic Freejet Quantum Cascade Laser Measurements of 4

Supersonic Free-jet Quantum Cascade Laser Measurements of 4 for CF 335 Cl and CF 337 Cl and FTS Measurements from 450 to 1260 cm-1 June 20, 2008 James F. Kelly, Thomas A. Blake, Robert L. Sams Pacific Northwest National Laboratory Richland, WA Arthur Maki Mill Creek, WA

Line-of-Sight Free Space Communications detector quantum cascade laser gas cell atmosphere, fog, aerosols, turbulence > km distances Lock laser on side of transition. Apply blue then red (“ 1”) or red then blue (“ 0”) FM chirp for bit transmission. Use gas to demodulate laser signal: FM to AM conversion at detector. Use laser wavelength that is less susceptible to atmospheric scattering effects. Provides secure, line-of-sight communications. Need a strong absorber in atmospheric window with sharp rovibrational transitions. 2

Fundamental Vibrational States (cm-1) of CF 3 Cl Fundamental CF 335 Cl 1 (a 1) 1108. 356 2 (a 1) 783. 362 3 (a 1) 476. 968 4 (e) 1216. 758 5 (e) 561. 109 6 (e) 347. 2 CF 337 Cl 1108. 026 782. 208 469. 165 1216. 720 560. 822 3

Ground State Constants (cm-1) of CF 3 Cl A B DJ 108 DJK 108 DK 108 CF 335 Cl 0. 191 3 a 0. 111 263 458 b 1. 843 98 b 6. 929 7 b 4. 123 a CF 337 Cl 0. 191 3 a 0. 108 461 01 b 1. 759 3 b 6. 724 4 b 4. 123 a a) Amrein, et al. Chem. Phys. Lett. 139 82 -88 (1987). b) Carpenter, et al. J. Mol. Spec. 93 286 -306 (1982). Vibrational assignments checked against ground state combination differences, F 2. 4

Experiment Chlorotrifluoromethane (CF 3 Cl, Freon-13) purchased from Syn. Quest Labs. Quantum cascade laser, pulsed, slit-jet molecular beam l l l Laser covers 1215. 8 to 1220. 6 cm-1 of 4 band. 0. 1% CF 3 Cl in Ar, backing pressure 100 to 1000 Torr. 12 cm x 200 mm, 7. 5 m. S pulse duration at 2. 88 Hz. Fourier transform spectra of CF 3 Cl l 1, 2 5, 4 bands: l 2, 2 3 bands: l 5 band: 20 cm path, 25 & -67 °C 0. 0018 cm-1 resolution. 20 cm path, 25 °C 3. 2 m path, 22 °C 0. 0013 cm-1 resolution. 9. 6 m, 22. 4 m path, 22 °C 0. 004 cm-1 resolution. 5

6

7

8

9

Term Value Expression: F(J, k, l) = G(v, l ) + Bv J(J+1) + (Av Bv) k 2 kl [ 2 A v Jv J(J+1) kvk 2 JJv J 2(J+1)2 JKv J(J+1)k 2 KKvk 4] DJv J 2(J+1)2 DJKv J(J+1)k 2 DKv k 4 + HJv. J 3(J+1)3 + HJKv. J 2(J+1)2 k 2 + HKJv. J(J+1)k 4 + HKvk 6 l-type Resonance Hamiltonian: W 2, 2 = v 4, J, k, l | H/hc | v 4, J, k 2, l 2 = ¼ {q 4 + q. J 4 J(J+1) + q. K 4 [k 2 + (k 2)2 ]} {(v 4+1)2 (l 1)2}½ {[ J (J + 1) k (k 1)][ J (J + 1) (k 1)(k 2)]}½ 10

4 Band Use work of Amrein et al. Chem. Phys. Lett. 139 82 -88 (1987) as starting point: J ≤ 20, K ≤ 20. Jet spectra improve assignment and fit in the Qbranch region. Present FTS measurements extend out to J = 76 and K = 49. Intensity alternation and ground state combinations used to verify assignments. 11

Rovibrational Constants (cm-1) for the 4 Band 0 A 103 B 103 DJ 108 DJK 108 DK 108 A J 106 K 106 q 4 103 q. J 4 108 Jet spectrum: No. lines Rms dev. FTS spectrum: Jmax Kmax No. of lines Rms. Dev. CF 335 Cl 1216. 758 284(12) 0. 751 04(4) 0. 003 797(21) 0. 061 3(7) 0. 203 8(24) 0. 218 1(32) 0. 151 052 4(4) 0. 338 2(5) 0. 094 7(9) 0. 195 38(11) 0. 144(4) CF 337 Cl 1216. 719 91(3) 0. 752 52(21) 0. 005 89(14) 0. 066(11) [ 0. 20] [0. 22] 0. 151 035 6(20) 0. 303 7(62) [ 0. 095] 0. 181 54(24) [ 0. 14] 339 0. 00022 231 0. 00023 76 49 4060 0. 00020 41 20 559 0. 00021 12

P 0 = 100 Torr 0. 1% CF 3 Cl in Ar 12 cm x 200 mm slit 7. 5 m. S gas pulse duration 2. 88 Hz gas pulse rate 0. 038 cm-1/m. S laser sweep Single sweep Laser power 45 m. W a. b. c. d. PR 3(10) 1219. 4067 cm-1 RR (16) 1219. 4288 cm-1 6 RR (14) 1219. 4344 cm-1 3 RR (12) 1219. 4454 cm-1 0 13

1 and 2 5 Coupling Term Crossing levels: J = 29, K = 18 level of 1 and J = 29, K = 16, l = -2 of 2 5 J = 46, K = 19 level of 1 and J = 46, K = 17, l = -2 of 2 5 …and higher K values. Coupling through a k = ± 2, l = ± 2 matrix element … v 1, v 5, J, k, l 5 | H/hc | v 1 1, v 5+2, J, k 2, l 5 2 = {c 2, 2 + ck 2, 2 [k 2+(k 2)2]} {[J(J+1) k(k 1)][J(J+1) (k 1)(k 2)]}½ 14

1 Band Giorgianni et al. J. Mol. Spec. 130 183 -192 (1988) extended diode laser measurements out to J = 65 for the 1 band. Our measurements go to J = 86 and K = 33. High density of lines and perturbations prevented assignments and fitting of higher transitions. No Q-branch lines used in fit. Only well resolved Pand R-branch lines were included in fit. Transitions with K < 5 not included in fit. 15

2 5 Band 2 5 consists of a parallel band with l = 0 and a perpendicular band with l = 0 and l = ± 2. The l = ± 2 levels are too weak to see. The perturbations of 1 = 1 are caused by an avoided crossing with the kl < 0 rotational manifold of 2 5. Only R-branch transitions were observed because the P-branch transitions overlapped with 1 band. Fit of the A component indicated that the E component is ~1 cm-1 lower. 16

Rovibrational Constants (cm-1) for CF 335 Cl 1 0 A 103 B 103 DJ 108 DJK 108 DK 108 HJ 1012 HJK 1012 HKJ 1012 HK 1012 A q 5 104 c 2, 2 104 c. K 2, 2 107 No. of lines Rms dev. 2 50 2 52 1108. 356 41(4) 1122. 854 15(6) 1121. 785(10) 0. 380 23(28) 0. 378 76(40) [ 0. 37876] 0. 566 97(5) 0. 095 05(10) [0. 09505] 0. 103 4(18) 0. 233 0(35) [ 0. 233] 0. 483(11) 0. 543(18) [0. 543] 1. 92(6) 0. 211(46) [ 0. 211] 0. 062 5(19) 0. 439(16) 2. 50(8) 15. 2(4) 0. 131 28(14) [1. 34] 0. 211(5) 0. 093(6) 2746 0. 00022 514 0. 00025 17

Rovibrational Constants (cm-1) for CF 337 Cl 1 0 A 103 B 103 DJ 108 DJK 108 DK 108 HJ 1012 HJK 1012 HKJ 1012 HK 1012 A q 5 104 c 2, 2 104 c. K 2, 2 107 1108. 025 93(8) 0. 387 58(41) 0. 544 35(15) 0. 123(7) 0. 254(32) 3. 04(5) [0. 06] [0. 43] [ 2. 5] [ 15. 2] [0. 211] [ 0. 093] No. of lines Rms dev. 711 0. 00025 2 50 1122. 299 64(21) 0. 385 7(12) 0. 088 02(32) [ 0. 245] [0. 596] [ 0. 163] [ 0. 131 28] [1. 34] 2 52 1121. 214 8(12) [ 0. 3857] [0. 08802] [ 0. 245] [0. 596] [ 0. 163] 34 0. 00041 18

19

3 State and 2 3 Band 3 band is very weak. Burger et al. J. Mol. Spec. 93 55 -73 (1982) gives band origin of 3 at 476. 973(7) cm-1 from 0. 04 cm-1 resolution spectra. Use the 1 – 3 difference band 2 + 3 – 3 hot band to determine 3 state constants. For the 2 3 band the K structure in the P- and R-branches is sharply peaked; assume the maximum is at K = 2. For the Q-branch the most intense transitions are K = J; assume peak is highest K value divisible by 3. 2 3 band of CF 337 Cl band was too weak to get full assignment, but could determine band origin. 20

Rovibrational Constants (cm-1) for 3 and 2 3 0 952. 406 16(8)a A 103 0. 060 59(25) B 103 0. 140 936(39) DJ 108 [0. 072] DJK 108 0. 349(33) DK 108 0. 334(32) No. of lines Rms. Dev. 215 0. 00028 CF 335 Cl 3 476. 967 54(7) 0. 029 28(28) 0. 067 30(6) 0. 036 9(11) 0. 126(8) 0. 003(30) 710 0. 00025 2 3 936. 943 61(21) [ 0. 055 0] 0. 135 40(19) [0. 072] [ 0. 36] [0. 32] 41 0. 00041 CF 337 Cl 3 469. 164 85(11) 0. 027 9(14) 0. 064 56(11) 0. 050 1(23) [ 0. 12] [0. 00] 129 0. 00029 21

22

2 Band Previous results from diode laser measurements of Baldacchini et al. J. Mol. Spec. 130 337 -343 (1988). K structure in R-branch not resolved; assume K = 2 for these transitions. K structure in P-branch partially resolved down to J = 25 for CF 335 Cl and J = 50 for CF 337 Cl. For resolved J structure in P-branch only strong transitions up to K = 48 with K divisible by 3 were used in fit. Low-J Q-branch transitions were assumed to be the largest K value possible divisible by 3. 23

Rovibrational constants (cm-1) for 2 and 2+ 3 3 2 CF 335 Cl 0 783. 362 065(35) A 103 0. 156 530(52) B 103 0. 168 814(15) DJ 1010 0. 073(12) DJK 1010 0. 99(14) DK 1010 4. 31(14) No. of lines Rms. Dev. 841 0. 00020 2+ 3 3 CF 337 Cl 2 781. 773 09(6) 782. 208 49(7) 0. 156 52(16) 0. 156 54(9) 0. 170 377(14) 0. 163 071(17) [ 0. 073] [ 0. 99] [4. 31] 175 0. 00026 268 0. 00032 24

25

26

5 Band RQ 0 -branch is sharper than other Q-branches because of large q 5 value. Band center agrees with results of Burger et al. Spectrochim. Acta 39 A 985 -992 (1983); B 5 and q 5 values agree with m-wave results of Carpenter et al. J. Mol. Spec. 93 286 -306 (1982). Most Q-branches resolved for J > 20. P- and Rbranches are resolved up to kl = +16. High density of lines made it difficult to assign the CF 337 Cl transitions. 27

Rovibrational Constants (cm-1) for 5 CF 335 Cl 0 A 103 B 103 DJ 108 DJK 108 DK 108 A J 106 K 106 JJ 1012 JK 1012 q 5 104 q. J 109 q. K 109 Jmax Kmax No. of lines Rms dev. 561. 108 935(12) 0. 184 774(25) [0. 076 442 9]c 0. 011 68(16) 0. 002 26(90) 0. 082 92(92) 0. 140 514 79(59) 0. 016 5(10) 0. 406 1(11) 0. 85(18) 1. 27(27) [0. 946 718 28] 0. 038(11) 15. 1(15) 86 70 5653 0. 00025 CF 337 Cl 560. 822 21(29) 0. 190 5(6) 0. 076 67(28) 0. 056(7) [ 0. 0022] [ 0. 082] 0. 141 041 2(35) [0. 0165] [ 0. 406] [0. 85] [ 1. 27] [0. 946718] [ 0. 038] [ 15. 1] 66 28 259 0. 00052 28

Summary Improved spectroscopic constants for the 4 band using combined QC-laser and jet spectra. Extend J and K values in FTS spectra. Improved spectroscopic constants for the 1 and 2 5 bands. Extend J and K values in FTS spectra. First rotationally resolved infrared measurement of 5 band. Improved spectroscopic constants for 2 and 2 + 3 – 3 hot band. Extend J and K values in FTS spectra. Use 1 – 3 and 2 + 3 – 3 to determine spectroscopic constants for 3 for the first time. 29