Abstract There is increasing interest in cold heavy polar molecular species for their applications in fundamental physics, such as the tests of the electron’s electric dipole moment. Here we propose a switched ring Stark decelerator suitable for slowing both light and heavy polar molecules. Two typical polar molecular species, ND 3 and 205 TlF, are employed to test the feasibility of our scheme with the help of trajectory calculation. Our proposed scheme is found to share many advantages with the state-of-the-art traveling wave decelerator, yet with relatively simple electronics and flexible operation modes. Sub-millikelvin molecular samples can be conveniently obtained in our decelerator using a combined operation mode. These monochromatic beams are ideal starting points for precise studies of molecular collision, cold chemistry and high-resolution spectroscopy.
Abstract There is increasing interest in cold heavy polar molecular species for their applications in fundamental physics, such as the tests of the electron’s electric dipole moment. Here we propose a switched ring Stark decelerator suitable for slowing both light and heavy polar molecules. Two typical polar molecular species, ND 3 and 205 TlF, are employed to test the feasibility of our scheme with the help of trajectory calculation. Our proposed scheme is found to share many advantages with the state-of-the-art traveling wave decelerator, yet with relatively simple electronics and flexible operation modes. Sub-millikelvin molecular samples can be conveniently obtained in our decelerator using a combined operation mode. These monochromatic beams are ideal starting points for precise studies of molecular collision, cold chemistry and high-resolution spectroscopy.
The growing field of cold molecule physics has demonstrated many methods of quantum control for precision measurement and molecular interaction studies. One particular method is Stark deceleration, which uses electric field gradients to produce packets of slow polar molecules. Since Stark deceleration does not increase phase-space density, the efficiency of the deceleration process is critical in determining the final cold molecule density. This dissertation describes three different Stark deceleration techniques. The first type of deceleration is pulsed-pin deceleration. We use this technique to produce slow OH molecules that can be trapped for cold collision studies. A two photon state-selective detection system, which includes a 118 nm photon, is used to determine the density distribution of OH in the trap. We explore the advantages and limitations to creating 118 nm light. The second and third types of Stark deceleration are pulsed-ring and traveling-wave methods of running a ring-geometry decelerator. Ring-geometry decelerators present improved deceleration efficiencies due to the cylindrical symmetry of the electrodes and true three-dimensional confinement. The pulsed-ring mode of the ring decelerator uses commercial high-voltage switches to apply discrete pulses to the ring electrodes. The continuous operation mode of the ring decelerator uses varying sine-wave voltages to create a traveling Stark potential well and has proven to be incredibly challenging due to the analog high voltage requirements of the system. In order to bring ND3 seeded in krypton (∼415 m/s) down to rest in the laboratory, sine wave voltages with amplitudes up to ±10 kV, currents up to 500 mA, and a bandwidth of 30 kHz down to DC are required. We describe a high-voltage amplifier that can be used for traveling-wave deceleration. The traveling-wave Stark deceleration mode is then compared to the pulsed-ring Stark deceleration mode and cases where one mode is superior to another are discussed.
To meet some demands for realizing precise measurements of an electric dipole moment of electron (eEDM) and examining cold collisions or cold chemical physics, we have proposed a novel, versatile electrostatic Stark decelerator with an array of true 3D electric potential wells, which are created by a series of horizontally-oriented, U-shaped electrodes with time-sequence controlling high voltages (± HV) and two guiding electrodes with a constant voltage. We have calculated the 2D electric field distribution, the Stark shifts of the four lowest rotational sub-levels of PbF molecules in the X1(2)Π1/2(v = 0) electronic and vibrational ground states as well as the population in the different rotational levels. We have discussed the 2D longitudinal and transverse phase-space acceptances of PbF molecules in our decelerator. Subsequently, we have simulated the dynamic processes of the decelerated PbF molecules using the 3D Monte-Carlo method, and have found that a supersonic PbF beam with a velocity of 300 m s(-1) can be efficiently slowed to about 5 m s(-1), which will greatly enhance the sensitivities to research a parity violation and measure an eEDM. In addition, we have investigated the dependences of the longitudinal velocity spread, longitudinal temperature and bunching efficiency on both the number of guiding stages and high voltages, and found that after bunching, a cold packet of PbF molecules in the J = 7/2, MΩ = -7/4 state with a longitudinal velocity spread of 0.69 m s(-1) (corresponding to a longitudinal temperature of 2.35 mK) will be produced by our high-efficient decelerator, which will generate a high energy-resolution molecular beam for studying cold collision physics. Finally, our novel decelerator can also be used to efficiently slow NO molecules with a tiny electric dipole moment (EDM) of 0.16 D from 315 m s(-1) to 28 m s(-1). It is clear that our proposed new decelerator has a good slowing performance and experimental feasibility as well as wide applications in the field of precise measurements and cold molecule physics.
Abstract Taming more species of molecules with large density is a long-standing goal in molecular science. Heavy molecule (> 100 amu) is of particular interest for precision measurements. However, decelerating a fast-moving beam of heavy molecules to rest remains challenging for Zeeman deceleration. Additionally, the traditional approach of pulsed Zeeman decelerator suffers from serious molecular loss during deceleration, significantly limiting its potential applications. Herein, we present a ring-shaped traveling wave Zeeman decelerator (RTWZD) featured with true three-dimensional smoothly-moving magnetic potential wells that directly solve the above intractable problems. With this approach, not only the density of the molecule can be greatly increased but also the range of molecular species for Zeeman deceleration can be extended from light to heavy. The performance of the RTWZD is characterized with both the theoretical analysis and the numerical calculation, where a group of atoms and molecules such as 7Li, 32O2, 88Sr19F and 174Yb19F are employed as testers. Losses in the traditional Zeeman decelerator can be avoided, yielding more than two orders of magnitude improvement in molecular density. These characteristics of the RTWZD make it an ideal toolbox to produce cold and dense atomic/molecular samples, enabling promising prospects for cold collision, sympathetic cooling, and precision measurement.
Physicists have observed all the elementary particles predicted by the Standard Model. These particles, however, account for only 5% of the total mass-energy of the Universe. In the quest to solve the mystery of missing matter and to extend our knowledge about nature, a large number of experimental research programs are devoted to find a glimpse of New Physics. Table-top high precision measurements on molecules can contribute to these efforts in a manner complementary to high-energy experiments at colliders. In this thesis, we describe the operation of a traveling-wave Stark decelerator. This device is designed and constructed in order to slow down heavy polar molecules for various future explorations. Deceleration is achieved by manipulation of the molecules in controllable electric fields. We demonstrate in an experiment the successful operation of the Stark decelerator by slowing down a beam of SrF molecules to one-third of their initial velocity, thus removing almost 90% of the initial kinetic energy. We also reveal limiting conditions for this process. These results are of importance for many exciting experiments using heavy molecules in the near future. One relevant and promising example of such experiments is the search for a permanent electric dipole moment of the electron.
Abstract Stark deceleration is a technique that uses time-varying inhomogeneous electric fields to decelerate polar molecules for various molecular beam and trapping experiments. New ring-geometry Stark decelerators with continuously varying voltages offer a method to produce a more intense source of molecules than in the more typically used crossed-pin geometry Stark decelerators. However, this new technique, traveling-wave Stark deceleration, is more experimentally challenging due to the electronic requirements. A third method, pulsed-ring Stark deceleration, uses ring-geometry electrodes with high-voltage pulses to decelerate molecules. The discrete voltages make it easier to implement, and it is more efficient in certain situations due to an increased longitudinal potential gradient. Here, we present an experimental realization of a ring-geometry Stark decelerator using both continuously varying and discrete voltages. Using the pulsed-ring method, we demonstrate a newly accessible low-velocity regime for moderate peak voltages on ring electrodes. This opens up the opportunity to efficiently decelerate various molecular species using a medium length decelerator. A comparison of experimental and simulated results between traveling-wave and pulsed-ring Stark deceleration is presented along with a simple model for determining when each mode is more efficient.
Taming a broader range of molecular species with large density has been a long-standing goal in molecular science. Heavy molecules with masses greater than 100 amu are of particular interest for precision measurements. However, decelerating a fast-moving beam of such heavy molecules to rest remains challenging for Zeeman deceleration. Moreover, the traditional approach of pulsed Zeeman decelerator suffers from serious molecular loss during deceleration, significantly limiting its potential applications. Herein, we present a proposal of ring-shaped traveling wave Zeeman decelerator (RTWZD) featured with true three-dimensional smoothly moving magnetic potential wells that effectively solve the above intractable problems. With the RTWZD approach, not only can the density of the molecule be greatly increased but also the range of molecular species for Zeeman deceleration can be extended from light to heavy. The performances of the RTWZD are characterized by theoretical analysis and numerical simulations, utilizing a group of atoms and molecules such as 7Li,16O2,88Sr19F, and 174Yb19F as testers. Notably, losses encountered in the traditional Zeeman decelerator can be avoided, yielding more than two orders of magnitude improvement in molecular density. These characteristics of the RTWZD make it an ideal toolbox to produce cold and dense atomic/molecular samples, with promising prospects for cold collision, sympathetic cooling, and precision measurement.