Ultracold He*+Rb mixture experiment


We are working on an ultracold atomic mixture of metastable triplet He (He*) and Rb. Our cooling strategy is based on a dual-species MOT, simultaneous RF- and MW-induced forced evaporative cooling in a quadrupole magnetic trap and transfer to an 1557-nm single beam optical dipole trap. Recently, we have realized the very first ultracold He*+alkali mixture in an optical dipole trap. We will study interspecies Penning ionization and explore interspecies Feshbach resonances.


• An ultracold, optically trapped mixture of 87Rb and metastable 4He atoms
Flores, Mishra, Vassen, Knoop, Eur. Phys. J. D 71, 49 (2017) (open access)

• Quantum-state-controlled Penning-ionization reactions between ultracold alkali-metal and metastable helium atoms
Flores, Vassen, Knoop, Phys. Rev. A 94, 050701(R) (2016)

• Simple method for producing Bose-Einstein condensates of metastable helium using a single beam optical dipole trap
Flores, Mishra, Vassen, Knoop, Appl. Phys. B 121, 391 (2015) (open access) (pdf)

• Efficient production of a 87Rb F=2, mF=2 Bose-Einstein condensate in a hybrid trap
Mishra, Flores, Vassen, Knoop, Eur. Phys. J. D 69, 52 (2015) (open access) (pdf)

• Ultracold mixtures of metastable He and Rb: scattering lengths from ab initio calculations and thermalization measurements
Knoop, Zuchowski, Kedziera, Mentel, Pachulski, Mishra, Flores, Vassen, Phys. Rev. A 90, 022709 (2014)

Lab highlights

February 2016, Lifetime measurements of ultracold mixture in optical dipole trap

Time evolution of He* in the single beam optical dipole trap, both for a He*+Rb mixture that is stable against Penning ionization (h+C), and after flipping the spin of the He* atoms (h+A), showing a dramatic decrease of the trapping lifetime.

November 2015, Our first dual species hybrid trap signal!

TOF signal (He*) and absorption image (Rb) after loading in the hybrid trap together, about 4x104 atoms of each species with a lifetime exceeding 10 seconds. This is the very first ultracold He*+alkali mixture in an optical dipole trap!

For more highlights, check lab news


Adonis Flores (PhD)

Dr. Wim Vassen

Dr. Steven Knoop (from October 2016 @ KNMI)

Former members

Hari Prasad Mishra (2011-2015, PhD)

Tim Berrier (2015, Bachelor student)
Tim van Leent (2013, Bachelor student)

We are part of the Atoms, Molecules & Lasers group and the LaserLaB Amsterdam.


This research is funded by the Netherlands Organization for Scientific Research (NWO) via a VIDI grant (680-47-511) and the Dutch Foundation for Fundamental Research on Matter (FOM) via a Projectruimte grant (11PR2905).