Ultracold molecules and ultracold chemistry

Bell, Martin T.; Softley, T. P.

doi:10.1080/00268970902724955

Cited by 268 publications

(260 citation statements)

References 261 publications

(291 reference statements)

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“…In Table F. 4 we summarize the block diagonalization of the Hamiltonian matrix in an electric field according to V for all possible cases of non-zero dipole moment directions, i. e., all possible combinations of non-zero dipole-moment components in the principal axes of the inertial system. We note that the remaining symmetry can be higher for M = 0 than for M ̸ = 0.…”

Section: Appendix F Block Diagonalization Of the Hamiltonian Matrixmentioning

confidence: 99%

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CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields

Chang

Filsinger

Sartakov

et al. 2014

Computer Physics Communications

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a b s t r a c tThe Controlled Molecule Imaging group (CMI) at the Center for Free Electron Laser Science (CFEL) has developed the CMIstark software to calculate, view, and analyze the energy levels of adiabatic Stark energy curves of linear, symmetric top and asymmetric top molecules. The program exploits the symmetry of the Hamiltonian to generate fully labeled adiabatic Stark energy curves.CMIstark is written in Python and easily extendable, while the core numerical calculations make use of machine optimized BLAS and LAPACK routines. Calculated energies are stored in HDF5 files for convenient access and programs to extract ASCII data or to generate graphical plots are provided. Chang et al. / Computer Physics Communications 185 (2014) [339][340][341][342][343][344][345][346][347][348][349] Nature of problem: Calculation of the Stark effect of asymmetric top molecules in arbitrarily strong dc electric fields in a correct symmetry classification and using correct labeling of the adiabatic Stark curves. Program summary Solution method:We set up the full M matrices of the quantum-mechanical Hamiltonian in the basis set of symmetric top wavefunctions and, subsequently, Wang transform the Hamiltonian matrix. We separate, as far as possible, the sub-matrices according to the remaining symmetry, and then diagonalize the individual blocks. This application of the symmetry consideration to the Hamiltonian allows an adiabatic correlation of the asymmetric top eigenstates in the dc electric field to the field-free eigenstates. This directly yields correct adiabatic state labels and, correspondingly, adiabatic Stark energy curves. Restrictions:The maximum value of J is limited by the available main memory. A modern desktop computer with 16 GB of main memory allows for calculations including all Js up to a values larger than 100 even for the most complex cases of asymmetric tops. Running time:Typically 1 s-1 week on a single CPU or equivalent on multi-CPU systems (depending greatly on system size and RAM); parallelization through BLAS/LAPACK. For instance, calculating all energies up to J = 25 of indole (vide infra) for one field strength takes 1 CPU-s on a current iMac.

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Section: Appendix F Block Diagonalization Of the Hamiltonian Matrixmentioning

confidence: 99%

“…Over the last decade, the manipulation of the motion of molecules using electric fields has been revitalized [1][2][3][4][5]. Exploiting the Stark effect, large asymmetric-top polar molecules have been deflected [6], focused [7], and decelerated [8].…”

Section: Introductionmentioning

confidence: 99%

CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields

Chang

Filsinger

Sartakov

et al. 2014

Computer Physics Communications

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“…Since the first experimental demonstration of Stark deceleration in 1998 [1], several decelerators ranging in size and complexity have been constructed [2][3][4]. Applications of these controlled molecular beams are found in high-resolution spectroscopy, the trapping of molecules at low temperature, and advanced scattering experiments that exploit the unprecedented state-purity and/or velocity control of the packets of molecules emerging from the decelerator [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Multistage Zeeman decelerator for molecular-scattering studies

Cremers¹,

Chefdeville²,

Janssen³

et al. 2017

Phys. Rev. A

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We present a concept for a multistage Zeeman decelerator that is optimized particularly for applications in molecular beam scattering experiments. The decelerator consists of a series of alternating hexapoles and solenoids, that effectively decouple the transverse focusing and longitudinal deceleration properties of the decelerator. It can be operated in a deceleration and acceleration mode, as well as in a hybrid mode that makes it possible to guide a particle beam through the decelerator at constant speed. The deceleration features phase stability, with a relatively large six-dimensional phase-space acceptance. The separated focusing and deceleration elements result in an unequal partitioning of this acceptance between the longitudinal and transverse directions. This is ideal in scattering experiments, which typically benefit from a large longitudinal acceptance combined with narrow transverse distributions. We demonstrate the successful experimental implementation of this concept using a Zeeman decelerator consisting of an array of 25 hexapoles and 24 solenoids. The performance of the decelerator in acceleration, deceleration, and guiding modes is characterized using beams of metastable helium ( 3 S) atoms. Up to 60% of the kinetic energy was removed for He atoms that have an initial velocity of 520 m/s. The hexapoles consist of permanent magnets, whereas the solenoids are produced from a single hollow copper capillary through which cooling liquid is passed. The solenoid design allows for excellent thermal properties and enables the use of readily available and cheap electronics components to pulse high currents through the solenoids. The Zeeman decelerator demonstrated here is mechanically easy to build, can be operated with cost-effective electronics, and can run at repetition rates up to 10 Hz.

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“…Many simple reactions of these species have low or negligible activation barriers and are therefore well suited for the study of low temperature chemical dynamics 3 . Calculations for the benchmark system F + H 2 → HF + H suggest a remarkably large value for the zero-Kelvin limiting rate constant despite the existence of a barrier in the entrance channel of order E/k B = 400 K 11 .…”

Section: Introductionmentioning

confidence: 99%

Production of cold bromine atoms at zero mean velocity by photodissociation

Doherty

Bell

Softley

et al. 2011

Phys. Chem. Chem. Phys.

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The production of a translationally cold (T o 1 K) sample of bromine atoms with estimated densities of up to 10 8 cm À3 using photodissociation is presented. A molecular beam of Br 2 seeded in Kr is photodissociated into Br + Br* fragments, and the velocity distribution of the atomic fragments is determined using (2 + 1) REMPI and velocity map ion imaging. By recording images with varying delay times between the dissociation and probe lasers, we investigate the length of time after dissociation for which atoms remain in the laser focus, and determine the velocity spread of those atoms. By careful selection of the photolysis energy, it is found that a fraction of the atoms can be detected for delay times in excess of 100 ms. These are atoms for which the fragment recoil velocity vector is directly opposed and equal in magnitude to the parent beam velocity leading to a resultant lab frame velocity of approximately zero. The FWHM velocity spreads of detected atoms along the beam axis after 100 ms are less than 5 ms À1 , corresponding to temperatures in the milliKelvin range, opening the possibility that this technique could be utilized as a slow Br atom source.

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Ultracold molecules and ultracold chemistry

Cited by 268 publications

References 261 publications

CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields

CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields

Multistage Zeeman decelerator for molecular-scattering studies

Production of cold bromine atoms at zero mean velocity by photodissociation

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