Supersonic Free-jet Quantum Cascade Laser Measurements of 4 for CF 3 35 Cl and CF 3 37 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

2 Line-of-Sight Free Space Communications quantum cascade laser atmosphere, fog, aerosols, turbulence > km distances gas cell detector 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.

3 Fundamental Vibrational States (cm -1 ) of CF 3 Cl FundamentalCF 3 35 ClCF 3 37 Cl 1 (a 1 ) (a 1 ) (a 1 ) (e) (e) (e) 347.2

4 Ground State Constants (cm -1 ) of CF 3 Cl CF 3 35 Cl CF 3 37 Cl A a a B b b D J  b b D JK  b b D K  10 8  a  a a) Amrein, et al. Chem. Phys. Lett (1987). b) Carpenter, et al. J. Mol. Spec (1982). Vibrational assignments checked against ground state combination differences,  F 2 .

5 ExperimentExperiment Chlorotrifluoromethane (CF 3 Cl, Freon-13) purchased from SynQuest Labs. Quantum cascade laser, pulsed, slit-jet molecular beam Laser covers to cm -1 of 4 band. 0.1% CF 3 Cl in Ar, backing pressure 100 to 1000 Torr. 12 cm x 200  m, 7.5 mS pulse duration at 2.88 Hz. Fourier transform spectra of CF 3 Cl 1, 2 5, 4 bands: 20 cm path, 25 & -67 ° C cm -1 resolution. 2, 2 3 bands: 20 cm path, 25 ° C 3.2 m path, 22 ° C cm -1 resolution. 5 band: 9.6 m, 22.4 m path, 22 ° C cm -1 resolution.

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10 Term Value Expression: F(J,k,l) = G(v,l ) + B v J(J+1) + (A v  B v ) k 2  kl [ 2A  v   J v J(J+1)   k v k 2  JJ v J 2 (J+1) 2  JK v J(J+1)k 2  KK v k 4 ]  D J v J 2 (J+1) 2  D JK v J(J+1)k 2  D K v k 4 + H J v J 3 (J+1) 3 + H JK v J 2 (J+1) 2 k 2 + H KJ v J(J+1)k 4 + H K v k 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

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

12 Rovibrational Constants (cm -1 ) for the 4 Band CF 3 35 Cl CF 3 37 Cl (12) (3)  A  10 3  (4)  (21)  B  10 3  (21)  (14)  D J  (7) 0.066(11)  D JK  10 8  (24) [  0.20]  D K  (32) [0.22] A  (4) (20)  J  (5) (62)  K  10 6  (9) [  0.095] q 4  (11) (24) q J 4  10 8  0.144(4) [  0.14] Jet spectrum: No. lines Rms dev FTS spectrum: Jmax Kmax No. of lines Rms. Dev

13 a. P R 3 (10) cm -1 b. R R 6 (16) cm -1 c. R R 3 (14) cm -1 d. R R 0 (12) cm -1 P 0 = 100 Torr 0.1% CF 3 Cl in Ar 12 cm x 200  m slit 7.5 mS gas pulse duration 2.88 Hz gas pulse rate cm -1 /mS laser sweep Single sweep Laser power 45 mW

14 1 and 2 5 Coupling Term 1 and 2 5 Coupling Term  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 + c k 2,2 [k 2 +(k  2) 2 ]}  {[J(J+1)  k(k  1)][J(J+1)  (k  1)(k  2)]} ½ 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 …

15 1 Band 1 Band Giorgianni et al. J. Mol. Spec (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 P- and R-branch lines were included in fit. Transitions with K < 5 not included in fit.

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.

17 Rovibrational Constants (cm -1 ) for CF 3 35 Cl (4) (6) (10)  A  10 3  (28)  (40) [  ]  B  10 3  (5) (10) [ ]  D J  (18)  (35) [  0.233]  D JK  (11) 0.543(18) [0.543]  D K  10 8  1.92(6)  0.211(46) [  0.211]  H J  (19)    H JK  (16)    H KJ   2.50(8)    H K   15.2(4)   A    (14) q 5  10 4  [1.34] c 2,2  (5) c K 2,2  10 7  0.093(6) No. of lines Rms dev

18 Rovibrational Constants (cm -1 ) for CF 3 37 Cl (8) (21) (12)  A  10 3  (41)  (12) [  ]  B  10 3  (15) (32) [ ]  D J  (7) [  0.245] [  0.245]  D JK  (32) [0.596] [0.596]  D K  10 8  3.04(5) [  0.163] [  0.163]  H J  [0.06]    H JK  [0.43]    H KJ  [  2.5]    H K  [  15.2]   A   [  ] q 5  10 4  [1.34] c 2,2  10 4 [0.211] c K 2,2  10 7 [  0.093] No. of lines Rms dev

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20 3 State and 2 3 Band 3 State and 2 3 Band 3 band is very weak. Burger et al. J. Mol. Spec (1982) gives band origin of 3 at (7) cm -1 from 0.04 cm -1 resolution spectra. Use the 1 – 3 difference band and – 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 band of CF 3 37 Cl band was too weak to get full assignment, but could determine band origin.

21 Rovibrational Constants (cm -1 ) for 3 and 2 3 CF 3 35 Cl CF 3 37 Cl (8)a (7) (21) (11)  A  10 3  (25)  (28) [  ]  (14)  B  10 3  (39)  (6)  (19)  (11)  D J  10 8 [0.072] (11) [0.072] (23)  D JK  10 8  0.349(33)  0.126(8) [  0.36] [  0.12]  D K  (32)  0.003(30) [0.32] [0.00] No. of lines Rms. Dev

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23 2 Band 2 Band Previous results from diode laser measurements of Baldacchini et al. J. Mol. Spec (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 3 35 Cl and J = 50 for CF 3 37 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.

24 Rovibrational constants (cm -1 ) for 2 and  3 CF 3 35 Cl CF 3 37 Cl  (35) (6) (7)  A  10 3  (52)  (16)  (9)  B  10 3  (15)  (14)  (17)  D J   0.073(12) [  0.073] [  0.073]  D JK   0.99(14) [  0.99] [  0.99]  D K  (14) [4.31] [4.31] No. of lines Rms. Dev

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27 5 Band 5 Band R Q 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 39A (1983); B 5 and q 5 values agree with  -wave results of Carpenter et al. J. Mol. Spec (1982). Most Q-branches resolved for J > 20. P- and R- branches are resolved up to kl = +16. High density of lines made it difficult to assign the CF 3 37 Cl transitions.

28 Rovibrational Constants (cm -1 ) for 5 CF 3 35 Cl CF 3 37 Cl (12) (29)  A  10 3  (25)  (6)  B  10 3 [ ]c (28)  D J  (16) 0.056(7)  D JK  10 8  (90) [  ]  D K  10 8  (92) [  0.082] A   (59)  (35)  J  (10) [0.0165]  K  10 6  (11) [  0.406]  JJ  (18) [0.85]  JK   1.27(27) [  1.27] q 5  10 4 [ ] [ ] q J  10 9  0.038(11) [  0.038] q K  10 9  15.1(15) [  15.1] Jmax Kmax No. of lines Rms dev

29 SummarySummary 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 – 3 hot band. Extend J and K values in FTS spectra. Use 1 – 3 and – 3 to determine spectroscopic constants for 3 for the first time.