Dispersed Fluorescence Spectroscopy of H 2 CO in

Dispersed Fluorescence Spectroscopy of H 2 CO in a Free-Jet Expansion Kristin Ellsworth Hope College, Holland, MI Summer 2006

• PES’s model molecular structure, dynamics, and reactivity Energy Potential Energy Surfaces Reaction Coordinate

• PES’s model molecular structure, dynamics, and reactivity • Measuring vibrational states characterizes the PES Energy Potential Energy Surfaces Reaction Coordinate

Dispersed Fluorescence (DF) Spectroscopy • Excite single rovibronic level • Disperse fluorescence • Observe S 0 energy levels Elaser Efluorescence Evib = Elaser - Efluorescence

Experimental Setup • Every spectroscopy experiment involves three parts: Light, Molecules, and Detection

Dispersed Fluorescence Results

Signal to Noise • Signal to noise ratio ≈ 6000: 1 • Higher resolution, less thermal noise, and less scattered light than before

Summary of Assignments • Total assigned peaks in 4 DF spectra: 372 • Unique vibrational states: 207

Assignment Experiment Fit – Expt. 0 -0. 21 0. 00 0. 21 41 1166. 83 1167. 33 0. 50 61 1248. 93 1252. 01 3. 08 31 1500. 27 1499. 23 -1. 04 … … 31 42 61 5043. 96 5042. 18 -1. 78 11 42 5090. 51 5092. 04 1. 53 42 51 5140. 45 5141. 97 1. 52 23 5177. 45 5176. 84 -0. 61 … … 21 31 45 61 10161. 64 10163. 49 1. 84 23 42 51 10178. 56 10174. 43 -4. 13 21 45 51 10244. 71 10250. 36 5. 65 22 46 10302. 16 10302. 34 0. 18 … …

Polyad Model Fit • Polyad model includes: – Harmonic energy: – Anharmonic correction: – Resonance mixing of states: 2 26 5 k 26, 5 « 2 15 16 4 k 26, 5 « 5 26 3 • Fit of 207 states (0 – 12, 125 cm-1) to ωi, xij, and 5 resonances has a RMS deviation of 3. 79 cm-1

Acknowledgements • Dr. William F. Polik • Brian Lajiness • Hope College Chemistry Department • Research Corporation, HHMI • Research Corporation, Dreyfus Foundation, NSF