2

3 With UV irradiation: Cl 2 + h  2 Cl* Cl* + H 2 (v = 0)  HCl + H Cl* + matrix  Cl Cl + H 2 (v = 0)  no reaction With IR irradiation: H 2 (v = 0)  H 2 (v = 1) Cl + H 2 (v = 1)  HCl + H 360 cm  1

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5

6 J. Phys. Chem. A 113, 7621 (2009)

7 = =

 Previous work on Cl + H 2 (Anderson)  A few questions explored with a tunable IR laser:  Spectroscopy of Cl-H 2  Efficiencies in excitation at various bands of H 2  Is H 2 (v = 1) delocalized?  Formation of HCl vs. (HCl) 2  Reactivity of Cl* 8

9 Nd:YAG Laser He-Ne MCT 3 K target Photoacoustic Cell T=95% BS 2000  3100 cm  1 filter 4000 cm  1 cutoff filter FTIR Globar source power meter H2H sccm 5.00 sccm Cl 2 12 K pH 2 converter IR OPO/OPA Laser frequency scanning from 4000 cm  1 up HCl-increase Scan IR laser frequency 365 nm LED or 355 nm Laser

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11 IR laser pumping from 4135 cm － 1 upward

12 A. After 365 nm for 2 h B. HCl action spectrum A B

cm cm -1 HCl increase / a.u IR intensity / a.u Laser energy / mJ pulse (*6 min)5.1 (*20 min) Relative Efficiency Frequency bandwidth =1.3 cm -1 x3

IR laser at cm － 1 IR laser at cm － nm FTIR probe IR laser pump 14 IR bandwidth =0.25 cm -1 3 min 6 min

15 (HCl) n (HCl) 2 (HCl) 3 IR laser frequency bandwidth =0.25 cm -1 AB C After 365 nm for 2 hour

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17 Time 4230 cm nm overlapIR before uv pulsesUV before IR pulses 4230 cm nm

 The spectrum of Cl-induced Q 1 (0) and S 1 (0) lines are identified near / and cm  1.  Excitation of the Cl-induced Q 1 (0) line has an efficiency ~2 times that of the Q R (0) band.  Excitation of the Q R (0) band is delocalized.  Excitation of the Q R (0) band produced more dimers than excitation of the Cl-induced Q 1 (0) line.  Q 1 (0) + S 1 (0) less efficient? (more work)  How long do the vibrons survive? (more work) 18

Jen-Yu Wu Mohammed Bahou 19