Polar molecules in selected quantum states can be guided, decelerated, and trapped using electric fields created by microstructured electrodes on a chip. Here we explore how nonadiabatic transitions between levels in which the molecules are trapped and levels in which the molecules are not trapped can be suppressed. We use $^{12}\mathrm{C}$O and $^{13}\mathrm{C}$O ($a {}^{3}{\ensuremath{\Pi}}_{1},v=0$) molecules, prepared in the upper $\ensuremath{\Lambda}$-doublet component of the $J=1$ rotational level, and study the trap loss as a function of an offset magnetic field. The experimentally observed suppression (enhancement) of the nonadiabatic transitions for $^{12}\mathrm{C}$O ($^{13}\mathrm{C}$O) with increasing magnetic field is quantitatively explained.
Polar molecules in selected quantum states can be guided, decelerated, and trapped using electric fields created by microstructured electrodes on a chip. Here we explore how nonadiabatic transitions between levels in which the molecules are trapped and levels in which the molecules are not trapped can be suppressed. We use 12CO and 13CO (a3\ensuremathΠ1,v=0) molecules, prepared in the upper \ensuremathΛ-doublet component of the J=1 rotational level, and study the trap loss as a function of an offset magnetic field. The experimentally observed suppression (enhancement) of the nonadiabatic transitions for 12CO (13CO) with increasing magnetic field is quantitatively explained.
Polar molecules in selected quantum states can be guided, decelerated, and trapped using electric fields created by microstructured electrodes on a chip, as shown on p. 1799 by G. Santambrogio et al. Transitions between two of these quantum states can be induced while the molecules are on the chip. CO (a3Π1, v=0) molecules, prepared at the J=1 rotational level, are trapped and guided to the center of the chip. There, they undergo the J=2←J=1 rotational transition driven by narrow-band sub-THz (mm-wave) radiation and, after being guided off the chip, are state-selectively detected.
Polar molecules in selected quantum states can be guided, decelerated and trapped using electric fields created by microstructured electrodes on a chip. Here we demonstrate that transitions between two vibrational quantum states can be induced while the molecules are trapped above the chip. We use CO molecules, prepared in the J = 1 rotational level of the a 3Π1, v = 0 state and induce the transition to either the J = 1 or the J = 2 level in the vibrationally excited a 3Π1, v = 1 state with pulsed, narrowband IR radiation. First, the vibrational excitation is studied using CO molecules in a freely propagating molecular beam, in a well-defined homogeneous electric field. Then, we demonstrate that the IR radiation can be coupled to CO molecules that are trapped less than 50 µm above the chip by guiding molecules in the v = 0 level to the center of the chip where they are pumped to the v = 1 level. The molecules remain trapped and are then guided off the chip and state-selectively detected.
Polar molecules in selected quantum states can be guided, decelerated, and trapped using electric fields created by microstructured electrodes on a chip. Herein we explore how transitions between two of these quantum states can be induced while the molecules are on the chip. We use CO (a(3) Π(1) , v=0) molecules, prepared in the J=1 rotational level, and induce the J=2←J=1 rotational transition with narrow-band sub-THz (mm-wave) radiation. First, the mm-wave source is characterized using CO molecules in a freely propagating molecular beam, and both Rabi cycling and rapid adiabatic passage are examined. Then we demonstrate that the mm-wave radiation can be coupled to CO molecules that are less than 50 μm above the chip. Finally, CO molecules are guided in the J=1 level to the center of the chip where they are pumped to the J=2 level, recaptured, and guided off the chip.
An electrostatic lattice is composed of many micro-scale traps. It is a powerful tool for manipulating cold polar molecules on a chip with the help of the interaction between the dipole moment and the inhomogeneous electric field. To the best of our knowledge, the existing electrostatic lattice still suffers the nonadiabatic transition that will lead to the escape of molecules from the electrostatic trap. In the paper, we skillfully design the electrode structure to avoid the zero-field zone at the center of every single microtrap, and the nonadiabatic transitions can be prevented. First, we numerically calculate the distribution of the spatial electrostatic field. Then, the influences of voltages on the electric field intensity and the height of the trap center are investigated. We simulate of the trajectory of molecules using the Monte Carlo method and figure out the factors impacting the loading efficiency of our electrostatic lattice. At last, we discuss how the voltages and the loading positions affect the positional distribution of trapped molecules.
The subject of this thesis’s work is research of cold molecules on a microchip. On the one hand, cold and ultracold molecules might allow high- precision measurements of molecular properties and the determination of their behavior at the quantum level. On the other hand, one could try to study highly controlled chemical reactions or to build a quantum computer with their help. In the experiments presented here, electrically neutral, polar molecules in low-field-seeking states are trapped and decelerated on a microchip with the help of electric fields. This exploits the Stark effect: the energy level shift of atoms and molecules in an electric field. After manipulation on the chip the molecules can be detected quantum-state specifically via the REMPI method. At first, CO molecules were prepared in the upper Λ-doublet component of the a3Π1, v = 0, J = 1 state, trapped on the chip and get vibrationally excited by an infrared laser in the middle of the chip to the J = 1 or J = 2 rotational state of the vibrational state v = 1. This could be shown experimentally and was analyzed theoretically for molecules which were trapped at all times. Secondly, CO molecules were detected on the chip and the structure of previously trapped molecule clouds of several of the only 120 μm spaced traps was spatially resolved. For this purpose the chip was extended with an ion lens setup, which enabled the determination of the temperature of the clouds by following the free ballistic expansion of the molecules in time; either by comparing the data to trajectory simulations (T = 11 ± 1 mK) or by applying a ballistic expansion model (T = 13 ± 3.5 mK), comparable to the method used by the ultracold atom community. The spatial imaging enabled the observation of a phasespace manipulation scheme, which adiabatically expanded the molecules in the trap and significantly reduces their temperature to approximately one third of their initial value. The third goal was to trap ground state ammonia molecules, which should extend the trapping time and would show that also other molecules could be trapped on the chip. The ammonia isotopologues 14NH3, 14ND3, and 15ND3 in the |vInv = 1, J = 1,K = 1> state of the electronic ground state X were used. No signal could be measured from trapped molecules, which is attributed to large nonadiabatic transitions to untrappable quantum states, leading to severe trap loss. At last, a new chip- based Stark decelerator is presented, which is a miniaturized version of the so-called “traveling-wave” ring decelerator. This chip-based decelerator should be able to trap more molecules compared to the chip that was used so far, and due to improved electronics it should be able to decelerate molecules from molecular beam velocities of approximately 360 m/s down to a standstill, in contrast to large-scale traveling-wave decelerators so far. The chip is still in development to achieve operation with the full specification (voltage). Performance simulations show the usefulness of this design, which needs to be tested in experiments.
Trapping particles (atoms or molecules) allows long interaction time and therefore potentially high resolution in precision measurements. Moreover, the particles in the trap are thermally isolated from the outside world and can be cooled to very low temperatures. As a result, the atomic (or molecular) traps have been widely used in many research areas. However, the molecules in these traps exhibiting zero field in the trap center undergo nonadiabatic transitions, which is the major loss of particles. The loss of atoms in this type of trap seriously hinders the generation of the first BEC (Bose-Einstein condensates). In this paper, we propose a chip-based controllable Ioffe-type electrostatic mirotrap, in which nonadabatic loss can be avoided due to the non-zero electric field. The mirotrap is composed of a pair of L-typed gold wires, which is 1 m in height and deposited on a glass substrate. The non-zero potential well originated in the microsize electrodes offers a steep gradient enable to trap low-field-seeking state polar molecules. The electric field strength in the trap center can be changed in a wide range by adjusting the applied voltage or/and the widths of the electrodes. For instance, under the conditions in the paper, the electric field strength in the trap center can be changed from 0.15 to 5.5 kV/cm. The height of the potential well is about 10 m above the chip and can also be tuned in a large range by adjusting the parameters of the electrodes. Under the conditions in the paper, the height of the potential well can be adjusted from 6.0 to 17.0 m. The electric fields of the microtrap near the surface of the chip are calculated by using a finite element software. Monte-Carlo simulations of the loading and the trapping processes are also carried out in order to justify the feasibility of our scheme. Taking ND3 molecules for example, the loading efficiency of molecules as a function of longitudinal velocity of molecular packet is studied. Our proposed surface microtrap can be used not only for integrating the molecular chips but also for producing the quantum degenerate gas near the chip surface. It offers a platform for many research fields such as precision measurements, quantum computing, surface cold collisions and cold chemistry.