1. Rydberg Series of C 60 Osnabrück, Germany March 2002 Eleanor Campbell, Göteborg University & Chalmers, Sweden R.D. Levine, Fritz Haber Center, Hebrew University M. Boyle, K. Hoffmann, C.P.Schulz & I.V. Hertel

2. Max-Born-Institut, Mark Boyle 2 Experimental Introduction Intensity - 10 11 -10 13 W/cm 2 Wavelength- 800nm, 400nm, 660nm Bandwidth Limited Pulse Duration Chirp Observed Rydberg Structure in photo-electron spectra Excitation and ionization processes TnTn SnSn T2T2 S2S2 T1T1 S1S1 1 T 1u S0S0 0 1 2 3 4 5 6 7 8 IP=7,58eV Energy /eV Dipole allowed: S 0  S 2 1Ag1Ag 1 T 1g Photoelectron spectroscopy to study the energy redistribution of C 60

3. Max-Born-Institut, Mark Boyle 3 Intensity Dependence of Photoelectron Spectra  = 800 nm,  = 1.5 ps electron yield / log units 1.5x10 12 W/cm 2 e - -energy / eV 1 2 0.5 30 60 90 10 20 30 1 2 3 0 0,51,5 1 electron yield *10 4 / arb. units 1.1x10 12 W/cm 2 2.2x10 12 W/cm 2 3.6x10 12 W/cm 2 0 0 0 0

4. Max-Born-Institut, Mark Boyle 4 Wavelength Dependence of Binding Energy ***assuming 1-photon ionization IP

5. Max-Born-Institut, Mark Boyle 5 Bandwidth Limited Pulse Duration Electron Spectra Comparison  E*  =0.441 Rydberg spectra seen for pulse durations as short as 25 fs Indicates very fast population process  meas =  laser   decay   laser  radiative decay <<  laser Lifetimes of Rydberg states are 400 fs or longer

6. Max-Born-Institut, Mark Boyle 6 Photoelectron Spectra for two chirps Shift=energy bandwidth of laser IP

7. Max-Born-Institut, Mark Boyle 7 Experimental Summary Intensity - R.S. emerges from background in low intensity pulses Wavelength - indicate a non-resonant excitation process Pulse duration - indicates a very fast process Chirp - indicates electron emitted within one pulse duration

8. Max-Born-Institut, Mark Boyle 8 Modeling of Rydberg Series in C 60 4 812 -0.5 -4 -8 r [a.u.] -12 -1.5 0 Solved the Schrödinger Equation for the bound energies of C 60 assuming a simple two particle system the potential as shown below Resultant BE values were in agreement with literature values of Puska and Nieminen, Phys. Rev. A 47, 1181 (1993)

9. Max-Born-Institut, Mark Boyle 9 Solid points from Calculation Open points from fitting of exp. Results from Calculation and fitting l=5 l=7 l=9l=3 l=1

10. Max-Born-Institut, Mark Boyle 10 Next Experimental Steps 1.) Two color pump probe 4.) C 70, NC 59,... 2.) angular distribution of Rydberg electrons 3.) cold C 60 source

11. Max-Born-Institut, Mark Boyle 11 Comparison to C 70