arXiv subjects

G. Z. Iwata

Publications and source records attributed to G. Z. Iwata.

6 recordsLinked to original sources

arXiv2017

High-resolution optical spectroscopy with a buffer-gas-cooled beam of BaH molecules

Barium monohydride (BaH) is an attractive candidate for extending laser cooling and trapping techniques to diatomic hydrides. The apparatus and high-resolution optical spectroscopy presented here demonstrate progress toward this goal. A cryogenic buffer-gas-cooled molecular beam of BaH was constructed and characterized. Pulsed laser ablation into cryogenic helium buffer gas delivers $\sim1\times10^{10}$ molecules/sr/pulse in the X$^2Σ^+$ ($v''=0,N''=1$) state of primary interest. More than $1\times10^7$ of these molecules per pulse enter the downstream science region with forward velocities below 100 m/s and transverse temperature of 0.1 K. This molecular beam enabled high-resolution optical spectra of BaH in quantum states relevant to laser slowing and cooling. The reported measurements include hyperfine structure and magnetic $g$ factors in the X$^2Σ^+$, B$^2Σ^+$, and A$^2Π_{1/2}$ states.

physics.atom-ph↗

arXiv2015

Precise study of asymptotic physics with subradiant ultracold molecules

Weakly bound molecules have physical properties without atomic analogues, even as the bond length approaches dissociation. In particular, the internal symmetries of homonuclear diatomic molecules result in formation of two-body superradiant and subradiant excited states. While superradiance has been demonstrated in a variety of systems, subradiance is more elusive due to the inherently weak interaction with the environment. Here we characterize the properties of deeply subradiant molecular states with intrinsic quality factors exceeding $10^{13}$ via precise optical spectroscopy with the longest molecule-light coherent interaction times to date. We find that two competing effects limit the lifetimes of the subradiant molecules, with different asymptotic behaviors. The first is radiative decay via weak magnetic-dipole and electric-quadrupole interactions. We prove that its rate increases quadratically with the bond length, confirming quantum mechanical predictions. The second is nonradiative decay through weak gyroscopic predissociation, with a rate proportional to the vibrational mode spacing and sensitive to short-range physics. This work bridges the gap between atomic and molecular metrology based on lattice-clock techniques, yielding new understanding of long-range interatomic interactions and placing ultracold molecules at the forefront of precision measurements.

physics.atom-ph↗

arXiv2015

High-precision spectroscopy of ultracold molecules in an optical lattice

The study of ultracold molecules tightly trapped in an optical lattice can expand the frontier of precision measurement and spectroscopy, and provide a deeper insight into molecular and fundamental physics. Here we create, probe, and image microkelvin $^{88}$Sr$_2$ molecules in a lattice, and demonstrate precise measurements of molecular parameters as well as coherent control of molecular quantum states using optical fields. We discuss the sensitivity of the system to dimensional effects, a new bound-to-continuum spectroscopy technique for highly accurate binding energy measurements, and prospects for new physics with this rich experimental system.

physics.atom-ph↗

arXiv2015

Control of Optical Transitions with Magnetic Fields in Weakly Bound Molecules

In weakly bound diatomic molecules, energy levels are closely spaced and thus more susceptible to mixing by magnetic fields than in the constituent atoms. We use this effect to control the strengths of forbidden optical transitions in $^{88}$Sr$_2$ over 5 orders of magnitude with modest fields by taking advantage of the intercombination-line threshold. The physics behind this remarkable tunability is accurately explained with both a simple model and quantum chemistry calculations, and suggests new possibilities for molecular clocks. We show how mixed quantization in an optical lattice can simplify molecular spectroscopy. Furthermore, our observation of formerly inaccessible $f$-parity excited states offers an avenue for improving theoretical models of divalent-atom dimers.

physics.atom-ph↗

arXiv2015

BaH molecular spectroscopy with relevance to laser cooling

We describe a simple experimental apparatus for laser ablation of barium monohydride (BaH) molecules and the study of their rovibrational spectra that are relevant to direct laser cooling. We present a detailed analysis of the properties of ablation plumes that can improve the understanding of surface ablation and deposition technologies. A range of absorption spectroscopy and collisional thermalization regimes has been studied. We directly measured the Franck-Condon factor of the $\mathrm{B}^2Σ^+(v'=0)\leftarrow\mathrm{X}^2Σ^+(v"=1)$ transition. Prospects for production of a high luminosity cryogenic BaH beam are outlined. This molecule is a promising candidate for laser cooling and ultracold fragmentation, both of which are precursors to novel experiments in many-body physics and precision measurement.

physics.atom-ph↗

arXiv2012

Small-sized Dichroic Atomic Vapor Laser Lock (DAVLL)

Two, lightweight diode laser frequency stabilization systems designed for experiments in the field are described. A significant reduction in size and weight in both models supports the further miniaturization of measurement devices in the field. Similar to a previous design, magnetic-field lines are contained within a magnetic shield enclosing permanent magnets and a Rb cell, so that these DAVLL systems may be used for magnetically sensitive instruments. The Mini-DAVLL system (49 mm long) uses a vapor cell (20 mm long), and does not require cell heaters. An even smaller Micro-DAVLL system (9mm long) uses a micro-fabricated cell (3 mm square), and requires heaters. These new systems show no degradation in performance with regard to previous designs, while considerably reducing dimensions.

physics.atom-ph↗