Application of TimeResolved FourierTransform Infrared Spectroscopy to Photodissociation

Application of Time-Resolved Fourier-Transform Infrared Spectroscopy to Photodissociation Dynamics Yuan-Pern Lee, Department of Applied Chemistry and Institute of Molecular Science National Chiao Tung University, Hsinchu, Taiwan

Outline l Introduction of step-scan FTS l Emission mode – slit-jet system Photolysis of Fluoro-compound l Emission mode – flow system Cl + CH 3 SH, O(1 D) + CO l Absorption mode – White cell C 6 H 5 SO 2 and its reactions

The Michelson Interferometer

Step-scan Data Acquisition I x 1 x 2 x 3 x 4 x 5 x 6 x 7 t 1 t 2 t 3 t 4 t 5 t 6 time

Experimental Setup (Emission) 10 ns / 0. 1 s 0. 1 / 0. 25 cm-1

Photolysis of Vinyl Chloride h + Cl HCCH + H H H C Cl C 2 H 2 Cl + H HCCH + Cl HCCCl + H 2 H : CC + H 2 Cl : CCH 2 + HCl (3 -center) HCCH + HCl (4 -center)

Rotational Distribution of HCl (v)

HCl-elimination from C 2 H 3 Cl Bimodal rotational distribution of HCl(v) high J (3 -center) low J (4 -center) Trot 10, 000 K Trot 500 K Tvib 16, 000 K peaked at v' = 2 ratio 83 : 17 Evidence of “kick” from vinylidene acetylene Vibrational adiabaticity? J. Chem. Phys. 114, 160 (2001)

Photolysis of CF 2 CHCl at 193 nm F H C F : CCF 2 C Cl X h � : CCF 2 + HCl (3 -center) FCCCl + HF (4 -center) FCCF J. Chem. Phys. 117, 9785 (2002)

Configuration of twin slit jets

TR-FTS with Twin Slit Jets Slit-Jet

Comparison of rot. distribution jet theory flow REMPI

Photolysis of Fluorobenzene at 193 nm

HF Emission from C 6 H 5 F (jet) at 248 nm

Rotational populations of HF after photolysis of C 6 H 5 F/He ~30 m. Torr at 248 nm

Vibrational population of HF

Photolysis of C 6 H 5 F at 193 nm Nascent internal energy of HF Erot = 15 2 k. J mol-1 (17 2 k. J mol-1 ) Evib = 34 4 k. J mol-1 (37 4 k. J mol-1 ) Eava = 284 k. J mol-1; Etrans = 96 k. J mol-1; EHF = 48 k. J mol-1 (54 6 k. J mol-1 ) EC 6 H 4 = 140 k. J mol-1 (134 8 k. J mol-1 ? )

Photolysis of CH 3(C 6 H 4)F at 193 nm

14. 1 kcal mol-1 12. 8 kcal mol-1 109. 7 kcal mol-1 91. 3 kcal mol-1

PES for HF-elimination of o-Fluorotoluene

Transition States of CH 3(C 6 H 4)F Species CH 2 CHF (528 k. J) CF 2 CHCl (458 k. J) C 6 H 5 F (284 k. J) CH 3 C 6 H 4 F (251 k. J) RHF /Å Evib /k. J mol-1 Erot (expt) Erot (impulse) /k. J mol-1 Angle 1. 281 83± 9 (0. 157) 8. 2 (219 k. J) 1 -4 3. 9 1. 176 46± 6 (0. 100) 17. 0 (199 k. J) 20± 4 16 1. 08 34± 6 (0. 120) 32. 8 (56 k. J) 15± 4 14 1. 08 ~26± 5 (0. 103) 27. 0 (59 k. J) ~10± 2 11

IR emission from C 6 H 5 F irradiation at 248 nm

Dynamics in Bimolecular Reactions

Dynamics in Bimolecular Reactions • Products are not produced instantly – Needs collisions – Depends on rate coefficients • Rotational quenching might be substantial – Non-negligible after 1 s • Nascent vibrational populations – Less affected by quenching – Extrapolation to t = 0 might have errors

Previous Derivation of Rot. Distrib.

Rotational Temperatures of HCl (v = 1) from Cl + H 2 S J. Chem. Phys. 119, 4229 (2003)

Temporal Profiles of HCl (v = 1, 2) Model of fitting Cl + H 2 S HCl (v = 2) + HS k 2 Cl + H 2 S HCl (v = 1) + HS k 1 HCl (v = 2) HCl (v = 1) kq 2 HCl (v = 1) HCl (v = 0) kq 1

Comparison of Cl + H 2 S and Cl +CH 3 SH J. Chem. Phys. 120, 1792 (2004) Cl + H 2 S Cl + CH 3 SH fr 0. 12 0. 02 0. 10 0. 02 fv 0. 33 0. 07 0. 49 0. 10 H. . . Cl 1. 619 Å 1. 675 Å D-effect rate ~0. 50 little effect TS (adduct) longer short-lived

Transition States of Cl + CH 3 SH

Dynamics of the 1 O( D) +CO reaction

E-V energy transfer Long-lived CO 2* collision complex Harding/Weston. Flynn JCP 88, 3590 (1988)

Comparison of Literature Values on Efficiency n E-V energy transfer efficiency 40 % Slanger et al. (1974) Expt. 21 % Shortridge et al. (1976) Expt. 25 % Harding et al. (1988) Expt. 31 % Matsumi et al. (1994) Expt. 29 % Makoto et al. (1994) Expt. 29 % Tully (1974) Theor. 21 % Kinnersly (1979) Theor.

Comparison of CO Vibrational Distribution J. P. C. 1994, 98, 12641 -12645 Makoto Abe, Yousuke Inagaki, Larry Yousuke Inagaki, L. Springsteen, Yutaka. L. Matsumi, Larry Springsteen, and Masahiro Yutaka Matsumi, Kawasaki, Hiroto Tachikawa. Kawasaki, Masahiro Hiroto Tachikawa (●) experimental work; (○) trajectory calculation; (Δ) Harding et al. (□) Shortridge et al.

CO Rotational Distribution J. P. C. 1994, 98, 12641 -12645 Makoto Abe, Yousuke Inagaki, Larry L. Springsteen, Yutaka Matsumi, Masahiro Kawasaki, Hiroto Tachikawa

Infrared emission spectra of CO

Comparison with Abe et al.

Detection of Intermediates TR-FTS in absorption mode

Experimental Setup for TRS-Absorption

J. Chem. Phys. 120, 3179 (2004) Absorption of Cl 2 SO irradiated at 248 nm resolution = 1. 5 cm-1; laser fluence = 100 m. J cm-2 Cl 2 SO = 0. 35, Ar = 24. 4 Torr Cl 2 SO = 0. 35, Ar = 1. 5 Torr

Simulated spectrum of Cl. SO at 300 K - Simulated - Experiment Resolution = 0. 3 cm-1; A’/A”, B’/B”, C’/C” = 0. 9906, 0. 9993, 0. 9982 a-type/b-type = 1/0. 2; Jmax=120; temp. = 350 K

Photolysis of C 6 H 5 SO 2 Cl

C 6 H 5 SO 2 Cl irradiated at 248 nm in a static cell R = 0. 5 cm-1 after 248 nm irradiating for 2 min at 10 Hz C 6 H 5 SO 2 Cl = ~140 m. Torr

Transient absorption upon photolysis of C 6 H 5 SO 2 Cl at 248 nm C 6 H 5 SO 2 Cl / N 2 = 1 / 240 at P = 72 Torr Temp. = 80 C R = 2 cm-1 7 expt. ave. 0 -7 s A 1 : 1278. 2 cm-1 A 2 : 1087. 7 cm-1 S : 1361. 8 cm-1 (SO 2 s-str. ) static C 6 H 5 SO 2 Cl P : 1453. 5, 1403. 5, 1196. 4, 1088. 7 cm-1

Photolysis of C 6 H 5 SO 2 Cl C 6 H 5 SO 2 Reaction of C 6 H 5 with SO 2 C 6 H 5 SO 2 C 6 H 5 Cl C 6 H 5 + Cl C 6 H 5 Br C 6 H 5 + Br

Reaction of C 6 H 5 and SO 2 A 1 : 1278. 2 cm-1 ; A 2 : 1087. 7 cm-1 B 1 : 1391. 6 / 1408. 6 cm-1 ; B 2 : 1203. 4 cm-1 C 6 H 5 SO 2 Cl / N 2 T= 80 C R = 2 cm-1 7 expt. Ave. 0 - 7 s T = 25 C R = 4 cm-1 22 - 52 s C 6 H 5 Cl / SO 2 / N 2 = 1 / 14 / 100 at P = 59 Torr C 6 H 5 Br / SO 2 / N 2 = 1 / 10 / 150 at P = 63 Torr T = 25 C R = 1. 5 cm-1 8 expt. ave. 17 - 47 s

Possible products: C 6 H 5 SO 2 C 6 H 5 OSO C 6 H 4 SO 2

Prediction of harmonic frequencies by DFT calculation C 6 H 5 SO 2 1044. 9 (8. 3) / 1031. 6 (24) C 6 H 5 OSO C 6 H 4 SO 2 Exp. 1022. 1 (0. 9) 1017. 9 (1. 7) 1063. 5 (16) / 1048. 6 (21. 4) 1052. 4 (9. 8) 1053. 9 (9. 1) 1092. 2 (93) / 1071. 6 (56. 8) 1103. 4 (9. 4) 1146. 9 (0. 5) 1087. 7 1101. 2 (7. 9) / 1099. 6 (7. 2) 1153. 2 (170. 9) 1166. 5 (328) 1203. 4 1181. 1 (0. 1) / 1185. 3 (0. 2) 1175. 9 (1. 8) 1194. 8 (1. 3) / 1199. 1 (2. 0) 1187. 4 (14. 0) 1278. 4 (0. 9) 1193. 1 (33. 8) 1264. 1 (111)/ 1226. 8 (106) 1216. 1 (121. 7) 1325. 9 (203) 1278. 2 1333. 4 (0. 2) / 1330. 0 (0. 5) 1336. 0 (0. 2) 1366. 3 (20. 5) 1391. 6 ? 1364. 4 (2. 5) / 1347. 6 (2. 8) 1364. 9 (0. 8) 1448. 1 (20. 8) 1481. 1 (12) / 1479. 9 (10. 8) 1491. 0 (2. 6) 1482. 5 (23. 3) B 3 P 86 / P 3 LYP with aug-cc-p. VTZ B 3 P 86 with 6 -311 G**

Simulated spectrum of C 6 H 5 SO 2 simulation parameters A = 0. 11579 cm-1 B = 0. 03369 cm-1 C = 0. 02645 cm-1 A /A = 1. 007 B /B = 0. 997 C /C = 0. 997 Temp. = 300 K Jmax=130 b-type: c-type = 1 : 0. 3 T 0 = 1279. 3 cm-1

Reaction of C 6 H 5 Br + SO 2 + 248 nm C 6 H 5 + SO 2 (C 6 H 5 OSO) C 6 H 4 OSOH Reaction of C 6 H 5 Cl + SO 2 + 248 nm C 6 H 5 + SO 2 (C 6 H 5 OSO) C 6 H 4 OSOH C 6 H 5 SO 2 Br C 6 H 5 SO 2 Cl

temporal profile of C 6 H 5 Br + SO 2 at 248 nm C 6 H 4 OSOH 3619 -3586 cm-1 t =4. 6 103 s-1 t=4. 4 103 s-1 Bn Bn(3700) t =1. 3 104 s-1 CAn. H 6 t =3. 1 103 s-1 Cn 5 SO 2 C 6 H 5 SO 2 Br

Summary • Transient absorption bands at 1278 and 1088 cm-1, observed upon photolysis of C 6 H 5 SO 2 Cl at 248 nm, are assigned as the SO 2 stretching modes of C 6 H 5 SO 2. • Same bands were observed from reactions of C 6 H 5 with SO 2 using C 6 H 5 Cl and C 6 H 5 Br as precursors. • Additional transient absorption bands at 1203, 1408, and 3607 cm-1, observed upon reaction of C 6 H 5 with SO 2, might be due to C 6 H 4 SOH. • Kinetics formation of C 6 H 5 SO 2 and C 6 H 4 SOH are discussed.

SUMMARY Applications of Time-resolved FTIR Dynamics in Photolysis l 4 -center molecular elimination of HF Dynamics in Bimolecular Reactions l Cl + H 2 S/CH 3 SH, O(1 D) + CO Detection of Intermediates (absorption) l Cl. SO, Cl. CS, C 6 H 5 SO 2 Multiplex advantage

Acknowledgments Ministry of Education National Science Council IAMS, Academia Sinica Chia-Yan Wu, Li-Kang Chu Sherry Liao, Shen-Kai Yang