1. Patterns of Broken Patterns RWF, Barratt Park, Bryan Changala, Josh Baraban, John Stanton, and Anthony Merer

2. I have always loved perturbations Isolated State Patterns – Need to see the small stuff: reduced term value plot Broken Pattern: Isolated Perturbation – Level crossing – Failure of second-order perturbation theory Patterns of Broken Patterns – Diatomic molecule: multiple (e,v) ~ (e’,v’) level crossings – Polyads: matrix element and membership scaling rules – S 1 acetylene Broken Pattern of Broken Patterns – Proximity to isomerization path: S 1 in-plane trans-cis – Polyad scaling violation and K-staggering Pattern of Broken Patterns of Broken Patterns Advances in Laser and Computational Technology

3. BIG STUFF SMALL STUFF

4. Perturbation-Free and Perturbed Bands of SiO

5. Patterns of Broken Patterns Diatomic Molecule: Multiple Level Crossings Polyads: Membership and Scaling

6. Proc. Phys. Soc. A 63, 1132 (1950) Scaling: H ev,e’v’ = H ee’

7. Polyads One low-P polyad generates all higher-P polyads!

8. Acetylene: S 1 Electronic State

9. trans conformer of S 1 C 2 H 2 + + - - Near-prolate top: -Franck-Condon active from S 0 -Totally symmetric - Non-totally symmetric bends - Darling-Dennison resonance and Coriolis coupling form bending polyads: trans bend torsion cis bend Bryan Changala

10. B 2 Polyads Consists of (v 4,v 6 ) = (2,0), (1,1), and (0,2) vibrational levels Add some quanta in trans-bend (mode 3) – 3 n B 2 – Polyad pattern should be independent of n – Surprise! Broken pattern of broken patterns

11. Excitation in v 3 distorts bending polyads Steeves et. al., J. Mol. Spec., 256, 256, 2009.

12. New Patterns Emerge both approach zero at trans-cis saddle point. Modes 3 and 6 must both be excited. Mode 4 is a “spectator” mode.

13. Fitting the Barrier Height ½[E(v+1)+E(v)]-E(0) (cm -1 ) E(v+1)-E(v) (cm -1 ) E TS = 4695 ± 36 cm -1 E TS = 4852 ± 5 cm -1 E TS = 4592 ± 2 cm -1 Fits to Experimental 3 n 6 2 T 0 data

14. Spectator Modes ½[E(v+1)+E(v)]-E(0) (cm -1 ) E(v+1)-E(v) (cm -1 )

15. What took so long? Better experimental methods Advances in computation New ideas embodied in H eff models This is not your grandfather’s spectroscopy

16. Next Three Talks TG05 Josh Baraban TG06 Bryan Changala TG07 Anthony Merer