1. Rotational and Vibrational Energy Transfer from the First Overtone Stretch of Acetylene Keith Freel Jiande Han Michael C. Heaven

2. Purpose: Optically Pumped Molecular Gas Lasers R ~90% @ 3μmμm 80 cm 2 m CaF 2 window detector/ spectrometer R~ 90% @ 3μmμm C 2 H 2, 2 Torr ns OPO R (7) 00000 10100 (01002 10000 00032 01020 ) 3 μm A.V.V. Nampoothiri, A Ratanavis, N. Campbell, and W. Rudolph. Optics Express, 18(3), 2010, p1946.

3. Purpose: Optically Pumped Molecular Gas Lasers R ~90% @ 3μmμm 80 cm 2 m CaF 2 window detector/ spectrometer R~ 90% @ 3μmμm C 2 H 2, 2 Torr ns OPO R (7) 00000 10100 (01002 10000 00032 01020 ) 3 μm A.V.V. Nampoothiri, A Ratanavis, N. Campbell, and W. Rudolph. Optics Express, 18(3), 2010, p1946. 1)Total removal from 10100 rotational levels 2)Rotational Energy Transfer 3)Vibrational Energy Transfer To what states? How fast?

4. IR-UV-DR (Time Resolved) Spectroscopy Three types of experiments 1.UV scan 2.IR scan 3.Time delay scan (00000) 00 X  + g (10100) 00 Direct Excitation: (V”, J”, K”)  (V,J,K)  V’, J’, K’ Indirect Transfer: (V”, J”, K”)  (V,J,K) init  (V,J,K) final  (V’,J’,K’) A 1 A u (v 3 ’ + v 5 ’) LIF (v 1 v 2 v 3 v 4 v 5 ) l > 5 ns

5. Spectroscopy of Acetylene ” 1 ” 2 ” 3 ” 4 ” 5 +g+g +g+g +u+u gg uu Ground State X  + g (D ∞h ) First Excited State A 1  u (C 2h ) ' 1 CH sym str ' 2 CC stretch ' 3 trans bend ’ 4 torsion ' 5 CH anti str ‘ 6 cis bend agag agag agag auau bubu bubu 3372.85 cm -1 Watson. J Molec. Spec. 95, 1982, 101. Merer. Mol. Phys. 101(4-5), 2003, 663. 1974.32 cm -1 3288.39 cm -1 612.87 cm -1 730.33 cm -1 2880.5 cm -1 768.26 cm -1 2857.41 cm -1 764.91 cm -1 1047.55 cm -1 1386.9 cm -1 Tobiason. J. Chem. Phys. 99(2), 1993, 928. Herman et al. J. Phys. Chem. Ref. Data, Vol. 32, No. 3, 2003. Also MF07.

6. Experimental Setup LIF Flow Cell PMT Excimer pumped Dye Laser with Doubling Crystal Nd:Yag pumped OPO/OPA Computer Boxcar with Preamp Optics/Filters Pump 1.5  m Probe 250 nm Delay Generator ~ 0.1 Torr C 2 H 2

7. 1. UV Scan – 20 ns delay (00000) 00 X  + g (10100) 00 A 1 A u (v 3 ’ + v 5 ’) J=4 J=14 J=12 J=10 J=8 J=6 nm (Simulation - PGopher) P R Q(6)Q(10) Q(14) R-branch P(7) P(11) P(9)

8. J=4 J=14 J=12 J=10 J=8 J=6 nm (Simulation - PGopher) P R Q(6)Q(10) Q(14) R-branch P(6) P(10) P(8) 1. UV Scan – 220 ns delay (00000) 00 X  + g (10100) 00 A 1 A u (v 3 ’ + v 5 ’)

9. Density Of States cm -1 VibrationalRotational 0.3 states/cm -1 > 6 states/cm -1 Herman et al. J. Phys. Chem. Ref. Data, Vol. 32, No. 3, 2003. 10100

10. Vibrational Energy Transfer nm (UV Scan) (00000) 00 X  + g (10100) A 1 A u (v 1 ’ + v 3 ’) a = c 1 |00200> - c 2 |11020> b = c 2 |00200> + c 1 |11020> A-X b A-X a Band heads Obs. (Odd  J) Pumped J=8 Calc. PGopher 10100  X a + 41 cm -1 10100  X b + 53 cm -1 Herman et al. J. Phys. Chem. Ref. Data, Vol. 32, No. 3, 2003. Merer. Mol. Phys. 101(4-5), 2003, 663. g u g g

11. 2. IR Scan Experiment (00000) 00 X  + g (10100) 00 A 1 A u (v 3 ’ + v 5 ’) IR Scan UV Fixed R(13) P(15)

12. 3. Time Scan Total Removal From 10100 (J=2 – J=16) ns JK i /10 -10 (cm 3 s -1 ) +/- 0.3 Crim 27.6NA 47.9NA 66.5NA 88.48.2 108.68.5 128.89.0 148.810.9 168.78.8 I(t) = A exp (-K i nt) J. D. Tobiason, Ph.D. thesis, University of Wisconsin-Madison, 1992.

13. RET kinetics – measuring k if Jk i  J=14 /10 -10 (cm 3 s -1 ) +/- 0.3 148.6 (Total Removal) 20.7 41.0 61.3 8 101.4 121.7 161.3 180.9 200.5 N f (t)/No = I f (t) = (k if /K i )[1-exp(-K i nt)] K i = total removal rate from i k if = state to state removal rate from i to f 0 100 200 (ns)

14. 0 400 800 1200 1600 2000 2400 2800 3200 20 and 220 ns UV Scans with Simulation for assignment Background Considerations Q(16) Q(12) Q(8) Q(20)

15. 20 and 220 ns UV Scans with Simulation for assignment Background Considerations Q(16) Q(12) Q(8) Q(20) Payne. Z. Phys. Chem. 219, (2005) 601–633 Payne. J. Phys. Chem. A, Vol. 110(9), (2006) 3307

16. Conclusions IR-UV DR spectroscopy has been used to identify VET and RET Total removal rates were measured from the 10100 state and match previous measurements. VET to the 00200/11020 diad was observed. Measured State-to-State RET rates are too large due to complex ET pathways.

17. Thank You For Listening Advisor: Michael Heaven Postdoc Fellow: Jiande Han Group Members: Ivan Antinov, Beau Barker, Md. Humayun Kabir