Asymmetric Top Rotors in Electric Fields. II. Influence of Internal Torsions in Molecular Beam Deflection Experiments

Abstract External fields have been widely adopted to control and manipulate the properties of gas-phase molecular species. In particular, electric fields have been shown to focus, filter and decelerate beams of polar molecules. While there are several well-established approaches for controlling the velocity and quantum-state distribution of reactant molecules, very few of these methods have examined the orientation of molecules in the resulting beam. Here we show that a buffer gas cell and three-bend electrostatic guide (coupled to a time-of-flight set-up) can be configured such that 70% of ammonia molecules in the cold molecular beam are oriented to an external electric field at the point of detection. With a minor alteration to the set-up, an approximately statistical distribution of molecular orientation is seen. These observations are explained by simulations of the electric field in the vicinity of the mesh separating the quadrupole guide and the repeller plate. The combined experimental apparatus therefore offers control over three key properties of a molecular beam: the rotational state distribution, the beam velocity, and the molecular orientation. Exerting this level of control over the properties of a molecular beam opens up exciting prospects for our ability to understand what role each parameter plays in reaction studies.

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Determining the translational and internal temperatures of isolated metal clusters: A comprehensive approach based on molecular-beam-deflection experiments

Physical Review A ◽

10.1103/physreva.104.012820 ◽

2021 ◽

Vol 104 (1) ◽

Author(s):

Thomas M. Fuchs ◽

Filip Rivic ◽

Rolf Schäfer

Keyword(s):

Molecular Beam ◽

Metal Clusters ◽

Comprehensive Approach ◽

Beam Deflection

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Rotational Brownian Motion and Nonlinear Dielectric Relaxation of Asymmetric Top Molecules in Strong Electric Fields: The Langevin Equation Approach

Nonlinear Dielectric Phenomena in Complex Liquids - NATO Science Series II: Mathematics, Physics and Chemistry ◽

10.1007/1-4020-2704-4_3 ◽

2006 ◽

pp. 31-44 ◽

Cited By ~ 2

Author(s):

Yu. P. Kalmykov

Keyword(s):

Brownian Motion ◽

Dielectric Relaxation ◽

Electric Fields ◽

Langevin Equation ◽

Equation Approach ◽

Nonlinear Dielectric ◽

Strong Electric Fields ◽

Asymmetric Top ◽

Rotational Brownian Motion

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Level statistics for asymmetric-top rotors in strong electric fields

Zeitschrift für Physik D ◽

10.1007/s004600050062 ◽

1996 ◽

Vol 38 (1) ◽

pp. 45-49 ◽

Cited By ~ 7

Author(s):

T. P. Grozdanov ◽

R. McCarroll

Keyword(s):

Electric Fields ◽

Level Statistics ◽

Strong Electric Fields ◽

Asymmetric Top

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MAGNETISM IN TRANSITION-METAL CLUSTERS FROM THE ATOM TO THE BULK

Surface Review and Letters ◽

10.1142/s0218625x96000772 ◽

1996 ◽

Vol 03 (01) ◽

pp. 429-434 ◽

Cited By ~ 20

Author(s):

I.M.L. BILLAS ◽

A. CHÂTELAIN ◽

W.A. de HEER

Keyword(s):

Molecular Beam ◽

Magnetic Moments ◽

Beam Deflection ◽

Transition Metal Clusters ◽

Iron Cluster ◽

Iron Cobalt ◽

Nickel Clusters ◽

Magnetic Shell ◽

Superparamagnetic Clusters ◽

Cobalt And Nickel

Molecular beam deflection measurements of small iron, cobalt, and nickel clusters show how magnetism develops as the cluster size is increased from several tens to several hundreds of atoms for temperatures from 80 and 1000 K. Cluster magnetization is found to be superparamagnetic for rotationally warm clusters, where it follows the Langevin function. The magnetization of rotationally cold clusters is anomalous: it is strongly reduced and nonlinear with the applied field. For superparamagnetic clusters, the magnetic moments can be determined from the magnetization. We find that ferromagnetism occurs even for the smallest sizes: for clusters with less than about 30 atoms the magnetic moments are atom-like and as the size is increased up to 700 atoms they approach the bulk limit, with oscillations probably caused by surface-induced spin-density waves. The trends are explained in a magnetic shell model. The magnetic properties of iron cluster show anomalies, suggesting that a high moment to low moment crystallographic phase transition in Fe clusters occurs at relatively low temperatures.

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Defect profiling of semiconductor epilayers using positron beams

Canadian Journal of Physics ◽

10.1139/p89-048 ◽

1989 ◽

Vol 67 (4) ◽

pp. 275-282 ◽

Cited By ~ 20

Author(s):

Erik Tandberg ◽

Peter J. Schultz ◽

Geof C. Aers ◽

T. E. Jackman

Keyword(s):

Electric Fields ◽

Molecular Beam ◽

Positron Lifetime ◽

Multilayered Structures ◽

Electric Field Effects ◽

State Diffusion ◽

Γ Rays ◽

Defect Interactions ◽

Homoepitaxial Layers ◽

Steady State Diffusion

Over the last 10 years, positrons have been used as a tool to study and profile dilute concentrations of defects in solids. The two basic techniques involve the measurement of the positron lifetime and the Doppler broadening of the annihilation γ-rays. Only recently have positrons been used to profile defects in multilayered structures. We review the theory of positron–defect interactions and positron transport in silicon, and introduce a model used to profile defects and electric-field effects using the steady-state diffusion equation. An example is discussed that involves the modelling of defects and electric fields in homoepitaxial layers of silicon grown by molecular-beam epitaxy on Si(100) substrates. Finally we discuss the limitations of the modelling technique and future prospects.

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Application of Molecular Beam Deflection Time-of-Flight Mass Spectrometry to Peptide Analysis

Analytical Chemistry ◽

10.1021/ac030202o ◽

2003 ◽

Vol 75 (20) ◽

pp. 5512-5516 ◽

Cited By ~ 13

Author(s):

Rodolphe Antoine ◽

Isabelle Compagnon ◽

Driss Rayane ◽

Michel Broyer ◽

Philippe Dugourd ◽

...

Keyword(s):

Mass Spectrometry ◽

Molecular Beam ◽

Time Of Flight ◽

Beam Deflection ◽

Peptide Analysis ◽

Flight Mass Spectrometry

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Growth of Iii-Nitrides by Rf-Assisted Molecular Beam Epitaxy

MRS Proceedings ◽

10.1557/proc-512-387 ◽

1998 ◽

Vol 512 ◽

Cited By ~ 4

Author(s):

E. C. Piquette ◽

P. M. Bridger ◽

Z. Z. Bandić ◽

T. C. Mcgill

Keyword(s):

Electric Fields ◽

Molecular Beam ◽

Plasma Source ◽

Rf Plasma ◽

X Ray Diffraction ◽

Rocking Curve ◽

X Ray ◽

Wide Range ◽

Device Structures ◽

Hall Technique

ABSTRACTGaN, AlGaN, AIN were grown on (0001) A1203 substrates by MBE using a RF plasma source and employing an AIN buffer layer. The films were characterized by RHEED, AFM, and x-ray diffraction, and electrical properties were measured by Hall technique. RHEED observations indicate that the polarity of the films is likely predominantly N-face, although Ga-face inversion domains can be observed in some films by AFM. Symmetric x-ray rocking curve widths as low as 39 arcseconds are achieved for some layers, while asymmetric peaks show widths of 240–300 arcsec. Control of Si doping over a wide range is demonstrated, which is important for design of high power device structures. Gold Schottky barrier m-v-n+diodes were fabricated which achieve high reverse electric fields before edge breakdown.

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