title: Probing QED and fundamental constants through laser spectroscopy of vibrational transitions in HD(.).
abstract: The simplest molecules in nature, molecular hydrogen ions in the form of H2(+) and HD(+), provide an important benchmark system for tests of quantum electrodynamics in complex forms of matter. Here, we report on such a test based on a frequency measurement of a vibrational overtone transition in HD(+) by laser spectroscopy. We find that the theoretical and experimental frequencies are equal to within 0.6(1.1) parts per billion, which represents the most stringent test of molecular theory so far. Our measurement not only confirms the validity of high-order quantum electrodynamics in molecules, but also enables the long predicted determination of the proton-to-electron mass ratio from a molecular system, as well as improved constraints on hypothetical fifth forces and compactified higher dimensions at the molecular scale. With the perspective of comparisons between theory and experiment at the 0.01 part-per-billion level, our work demonstrates the potential of molecular hydrogen ions as a probe of fundamental physical constants and laws.
authors.affiliation: LaserLaB, Department of Physics and Astronomy, VU University, De Boelelaan 1081, Amsterdam 1081 HV, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Biesheuvel
authors.affiliation: Laboratoire Kastler Brossel, UPMC-Sorbonne Universités, CNRS, ENS-PSL Research University, Collège de France, 4 place Jussieu, Paris 75005, France.|Département de Physique, Université d'Evry Val d'Essonne, Boulevard François Mitterrand, 91025 Evry, France.
authors.forename: J-Ph
authors.initials: JP
authors.lastname: Karr
authors.affiliation: Laboratoire Kastler Brossel, UPMC-Sorbonne Universités, CNRS, ENS-PSL Research University, Collège de France, 4 place Jussieu, Paris 75005, France.|Département de Physique, Université d'Evry Val d'Essonne, Boulevard François Mitterrand, 91025 Evry, France.
authors.forename: L
authors.initials: L
authors.lastname: Hilico
authors.affiliation: LaserLaB, Department of Physics and Astronomy, VU University, De Boelelaan 1081, Amsterdam 1081 HV, The Netherlands.
authors.forename: K S E
authors.initials: KS
authors.lastname: Eikema
authors.affiliation: LaserLaB, Department of Physics and Astronomy, VU University, De Boelelaan 1081, Amsterdam 1081 HV, The Netherlands.
authors.forename: W
authors.initials: W
authors.lastname: Ubachs
authors.affiliation: LaserLaB, Department of Physics and Astronomy, VU University, De Boelelaan 1081, Amsterdam 1081 HV, The Netherlands.
authors.forename: J C J
authors.initials: JC
authors.lastname: Koelemeij
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