title: Observation of pendular butterfly Rydberg molecules.
abstract: Engineering molecules with a tunable bond length and defined quantum states lies at the heart of quantum chemistry. The unconventional binding mechanism of Rydberg molecules makes them a promising candidate to implement such tunable molecules. A very peculiar type of Rydberg molecules are the so-called butterfly molecules, which are bound by a shape resonance in the electron-perturber scattering. Here we report the observation of these exotic molecules and employ their exceptional properties to engineer their bond length, vibrational state, angular momentum and orientation in a small electric field. Combining the variable bond length with their giant dipole moment of several hundred Debye, we observe counter-intuitive molecules which locate the average electron position beyond the internuclear distance.
authors.affiliation: Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Niederprüm
authors.affiliation: Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.|Graduate School Materials Science in Mainz, Staudinger Weg 9, 55128 Mainz, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Thomas
authors.affiliation: Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.
authors.forename: Tanita
authors.initials: T
authors.lastname: Eichert
authors.affiliation: Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Lippe
authors.affiliation: Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Jesús
authors.initials: J
authors.lastname: Pérez-Ríos
authors.affiliation: Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Chris H
authors.initials: CH
authors.lastname: Greene
authors.affiliation: Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.
authors.forename: Herwig
authors.initials: H
authors.lastname: Ott
mesh_terms: D004560:Electricity; D004583:Electrons; D004738:Engineering; D008027:Light; D008280:Magnetics; D015233:Models, Statistical; D009038:Motion; D017785:Photons; D011789:Quantum Theory; D012399:Rotation; D013053:Spectrophotometry; D014732:Vibration