The Neumark Group


Department of Chemistry, University of California Berkeley
and Chemical Science Division, Lawrence Berkeley National Laboratory

Slow photoelectron velocity-map imaging spectroscopy

Fast beam translational spectroscopy

Femtosecond Time-resolved photoelectron imaging

Molecular beam photodissociation dynamics

Spectroscopy and dynamics in helium droplets

Attosecond spectroscopy

Spectroscopy and dynamics in liquid microjets

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Spectroscopy and dynamics in helium droplets


Liquid helium nanodroplets, consisting of on average 2 x 106 atoms per particle, are examined using a femtosecond time-resolved photoelectron imaging scheme. The droplets are initially excited by a pulse of 23.6(2) eV extreme ultraviolet (XUV) light in resonance with an electronically excited band associated with the 1s3p Rydberg level of a free He atom. Relaxation dynamics are probed by pulsed photoionization at 3.2 eV with velocity map imaging (VMI) used to measure energy distributions of the emitted electrons.

Several different relaxation channels have been been observed from the highly electronically excited initial state. These include ejection of Rydberg-excited atoms and clusters from the superfluid droplet environment as well as internal electronic dynamics within and among the excited bands. Our current efforts focus on examining the transfer of energy from the initially excited state to atomic and molecular dopants.

Molecules studied:

Helium nanodroplets

Information obtained:

Dynamics of electronic structure in the time and energy domains.

Project members:

Catherine Saladrigas

Recent publications:

♦ "Sizes of pure and doped helium droplets from single shot x-ray imaging" R. M. P. Tanyag, C. Bacellar, W. Pang, C. Bernando, L. F. Gomez, C. F. Jones, K. F. Ferguson, J. Kwok, D. Anielski, A. Belkacem, R. Boll, J. Bozek, S. Carron, G. Chen, T. Delmas, L. Englert, S. W. Epp, B. Erk, L. Foucar, R. Hartmann, A. Hexemer, M. Huth, S. R. Leone, J. H. Ma, S. Marchesini, D. M. Neumark,B. K. Poon, J. Prell, D. Rolles, B. Rudek, A. Rudenko, M. Seifrid, M. Swiggers, J. Ullrich, F. Weise, P, Zwart, C. Bostedt, O. Gessner, A. F. Vilesov J. Chem. Phys. 156, 041102 (2022). pdf

♦ "Charging and ion ejection dynamics of large helium nanodroplets exposed to intense femtosecond soft X-ray pulses" C. A. Sladrigas, A. J. Feinber, M. P. Ziemkiewicz, C. Bacellar, M. Bucher, C. Bernando, S. Carron, A. S. Chatterley, F.-J. Decker, K. R. Ferguson, L. Gomez, T. Gorkhover, N. A. Helvy, C. F. Jones, J. J. Kwok, A. Lutman, D. Rupp, R. M. P. Tanyag, T. Moller, D. M. Neumark, C. Bostedt, A. F. Vilesov, O. Gessner, Eur. Phys. J. Spec. Top. (2021). pdf

♦ "Ultrafast relaxation of photoexcited superfluid He nanodroplets" M. Mudrich, A.C. LaForge, A. Ciavardini, P. O'Keeffe, C. Callegari, M. Coreno, A. Demidovich, M. Devetta, M. Di Fraia, M. Drabbels, P. Finetti, O. Gessner, C. Grazioli, A. Hernando, D.M. Neumark, Y. Ovcharenko, P. Piseri, O. Plekan, K.C. Prince, R. Richter, M.P. Ziemkiewicz, T. Moeller, J. Eloranta, M. Pi, M. Barranco, F. Stienkemeier, Nat. Commun. 11, 112 (2020). pdf

♦ "Coupled motion of Xe clusters and quantum vortices in He nanodroplets" C. F. Jones, C. Bernando, R. M. P. Tanyag, C. Bacellar, K. R. Ferguson, L. F. Gomez, D. Anielski, A. Belkacem, R. Boll, J. Bozek, S. Carron, J. Cryan, L. Englert, S. W. Epp, B. Erk, L. Foucar, R. Hartmann, D. M. Neumark, D. Rolles, A. Rudenko, K. R. Siefermann, F. Weise, B. Rudek, F. P. Sturm, J. Ullrich, C. Bostedt, O. Gessner, A. F. Vilesov, Phys. Rev. B 93, 180510 (2016). pdf