scholarly journals Direct observation of transitions between quantum states with energy differences below 10 neV employing a Sona unit

2021 ◽  
Vol 75 (9) ◽  
Author(s):  
Ralf Engels ◽  
Markus Büscher ◽  
Paul Buske ◽  
Yuchen Gan ◽  
Kirill Grigoryev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Photon Energy ◽  
Atomic Beam ◽  
Hyperfine Splitting ◽  
Rest Frame ◽  
Quantum States ◽  
Direct Access ◽  
Spectroscopic Methods ◽  
Hydrogen Atoms ◽  
Atomic Transitions

Abstract The direct access to atomic transitions between close by quantum states employing standard spectroscopic methods is often limited by the size of the necessary radio-frequency cavities. Here we report on a new tool for fundamental spectroscopy measurements that can overcome this shortcoming. For this, a Sona transition unit was used, i.e., two opposed solenoidal coils that provide an oscillating field in the rest frame of the through-going atomic beam. In this way, we were able to control the induced photon energy down to 10 neV or $$f \sim $$ f ∼ MHz. The tuneable parameter is the velocity of the atomic beam. For illustration of the method, we report a measurement of the hyperfine splitting energies between the substates with $$F=1$$ F = 1 and $$m_F = -1, 0, +1$$ m F = - 1 , 0 , + 1 of $$2S_{1/2}$$ 2 S 1 / 2 metastable hydrogen atoms as function of a magnetic field. Graphic Abstract

MAGNETIC FIELD, PRESSURE AND TEMPERATURE DEPENDENT OPTICAL PROPERTIES IN A GaAs 9.0 P 1.0 QUANTUM DOT

2014 ◽  
Vol 6 (2) ◽  
pp. 1178-1190
Author(s):  
A. JOHN PETER ◽  
Ada Vinolin
Keyword(s):  
Magnetic Field ◽  
Optical Properties ◽  
Quantum Dot ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Photon Energy ◽  
Nonlinear Optical ◽  
Binding Energies ◽  
Nonlinear Optical Properties ◽  
Optical Rectification

Simultaneous effects of magnetic field, pressure and temperature on the exciton binding energies are found in a 9.0 1.0 6.0 4.0 GaAs P / GaAs P quantum dot. Numerical calculations are carried out taking into consideration of spatial confinement effect. The cylindrical system is taken in the present problem with the strain effects. The electronic properties and the optical properties are found with the combined effects of magnetic field strength, hydrostatic pressure and temperature values. The exciton binding energies and the nonlinear optical properties are carried out taking into consideration of geometrical confinement and the external perturbations.Compact density approach is employed to obtain the nonlinear optical properties. The optical rectification coefficient is obtained with the photon energy in the presence of pressure, temperature and external magnetic field strength. Pressure and temperature dependence on nonlinear optical susceptibilities of generation of second and third order harmonics as a function of incident photon energy are brought out in the influence of magnetic field strength. The result shows that the electronic and nonlinear optical properties are significantly modified by the applications of external perturbations in a 9.0 1.0 6.0 4.0 GaAs P / GaAs P quantum dot.

scholarly journals Energy Correlations of α-Particles in the 8Be-Nucleus Ground-State Formation Channel of the 12C(γ,3α) and 16O(γ,4α) Reactions

2019 ◽  
Vol 64 (9) ◽  
pp. 787
Author(s):  
S. N. Afanasyev
Keyword(s):  
Magnetic Field ◽  
Photon Energy ◽  
Relative Motion ◽  
Cross Sections ◽  
Ground State ◽  
Diffusion Chamber ◽  
Mechanism Of Interaction ◽  
The Magnetic Field ◽  
Maximum Photon ◽  
Α Particles

The method of diffusion chamber in the magnetic field making use of a bremsstrahlung beam with a maximum photon energy of 150 MeV is applied to study the 12C(y,3a) and 16O(y,4a) reactions. A resonance identified as the ground state of 8Be nucleus is found in the distribution of events over the energy of the relative motion of two a-particles. The partial cross-sections of the 8Be nucleus formation channels are measured. It is shown that the mechanism of interaction between a y-quantum and a virtual a-particle pair takes place in this case.

scholarly journals Foreshock cavitons and spontaneous hot flow anomalies: A statistical study with a global hybrid-Vlasov simulation

2021 ◽  
Author(s):  
Vertti Tarvus ◽  
Lucile Turc ◽  
Markus Battarbee ◽  
Jonas Suni ◽  
Xóchitl Blanco-Cano ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Rest Frame ◽  
Statistical Study ◽  
Plasma Temperature ◽  
Propagation Speed ◽  
Bow Shock ◽  
Ulf Waves ◽  
Subsequent Formation ◽  
Comparable Amount

Abstract. The foreshock located upstream of Earth's bow shock hosts a wide variety of phenomena related to the reflection of solar wind particles from the bow shock and the subsequent formation of ultra-low frequency (ULF) waves. In this work, we investigate foreshock cavitons, which are transient structures resulting from the non-linear evolution of ULF waves, and spontaneous hot flow anomalies (SHFAs), which evolve from cavitons as they accumulate suprathermal ions while being carried to the bow shock by the solar wind. Using the global hybrid-Vlasov simulation model Vlasiator, we have conducted a statistical study in which we track the motion of individual cavitons and SHFAs in order to examine their properties and evolution. In our simulation run where the interplanetary magnetic field (IMF) is directed at a sunward-southward angle of 45 degrees, continuous formation of cavitons is found up to ~ 11 Earth radii (RE) from the bow shock (along the IMF direction), and caviton-to-SHFA evolution takes place within ~ 2 RE from the shock. A third of the cavitons in our run evolve into SHFAs, and we find a comparable amount of SHFAs forming independently near the bow shock. We compare the properties of cavitons and SHFAs to prior spacecraft observations and simulations, finding good agreement. We also investigate the variation of the properties as a function of position in the foreshock, showing that the transients close to the bow shock are associated with larger depletions in the plasma density and magnetic field magnitude, along with larger increases in the plasma temperature and the level of bulk flow deflection. Our measurements of the propagation velocities of cavitons and SHFAs agree with earlier studies, showing that the transients propagate sunward in the solar wind rest frame. We show that SHFAs have a greater solar wind rest frame propagation speed than cavitons, which is related to an increase in the magnetosonic speed near the bow shock.

scholarly journals Foreshock cavitons and spontaneous hot flow anomalies: a statistical study with a global hybrid-Vlasov simulation

2021 ◽  
Vol 39 (5) ◽  
pp. 911-928
Author(s):  
Vertti Tarvus ◽  
Lucile Turc ◽  
Markus Battarbee ◽  
Jonas Suni ◽  
Xóchitl Blanco-Cano ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Rest Frame ◽  
Statistical Study ◽  
Plasma Temperature ◽  
Propagation Speed ◽  
Bow Shock ◽  
Ulf Waves ◽  
Subsequent Formation ◽  
Comparable Amount

Abstract. The foreshock located upstream of Earth's bow shock hosts a wide variety of phenomena related to the reflection of solar wind particles from the bow shock and the subsequent formation of ultra-low-frequency (ULF) waves. In this work, we investigate foreshock cavitons, which are transient structures resulting from the non-linear evolution of ULF waves, and spontaneous hot flow anomalies (SHFAs), which are thought to evolve from cavitons as they accumulate suprathermal ions while being carried to the bow shock by the solar wind. Using the global hybrid-Vlasov simulation model Vlasiator, we have conducted a statistical study in which we track the motion of individual cavitons and SHFAs in order to examine their properties and evolution. In our simulation run where the interplanetary magnetic field (IMF) is directed at a sunward–southward angle of 45∘, continuous formation of cavitons is found up to ∼11 Earth radii (RE) from the bow shock (along the IMF direction), and caviton-to-SHFA evolution takes place within ∼2 RE from the shock. A third of the cavitons in our run evolve into SHFAs, and we find a comparable amount of SHFAs forming independently near the bow shock. We compare the properties of cavitons and SHFAs to prior spacecraft observations and simulations, finding good agreement. We also investigate the variation of the properties as a function of position in the foreshock, showing that transients close to the bow shock are associated with larger depletions in the plasma density and magnetic field magnitude, along with larger increases in the plasma temperature and the level of bulk flow deflection. Our measurements of the propagation velocities of cavitons and SHFAs agree with earlier studies, showing that the transients propagate sunward in the solar wind rest frame. We show that SHFAs have a greater solar wind rest frame propagation speed than cavitons, which is related to an increase in the magnetosonic speed near the bow shock.

scholarly journals The ring current: a short biography

2012 ◽  
Vol 3 (2) ◽  
pp. 131-142 ◽  
Author(s):  
A. Egeland ◽  
W. J. Burke
Keyword(s):  
Magnetic Field ◽  
Ring Current ◽  
Energy Content ◽  
Spectral Characteristics ◽  
Direct Access ◽  
Sufficient Evidence ◽  
Mass Spectrometers ◽  
Before And After ◽  
Magnetic Signatures ◽  
Collective Plasma

Abstract. The "ring current'' grows in the inner magnetosphere during magnetic storms and contributes significantly to characteristic perturbations to the Earth's field observed at low-latitudes. This paper outlines how understanding of the ring current evolved during the half-century intervals before and after humans gained direct access to space. Its existence was first postulated in 1910 by Carl Størmer to explain the locations and equatorward migrations of aurorae under stormtime conditions. In 1917 Adolf Schmidt applied Størmer's ring-current hypothesis to explain the observed negative perturbations in the Earth's magnetic field. More than another decade would pass before Sydney Chapman and Vicenzo Ferraro argued for its necessity to explain magnetic signatures observed during the main phases of storms. Both the Størmer and Chapman–Ferraro models had difficulties explaining how solar particles entered and propagated in the magnetosphere to form the ring current. During the early 1950s Hannes Alfvén correctly argued that the ring current was a collective plasma effect, but failed to explain particle entry. The discovery of a weak but persistent interplanetary magnetic field embedded in a continuous solar wind provided James Dungey with sufficient evidence to devise the magnetic merging-reconnection model now regarded as the basis for understanding magnetospheric and auroral activity. In the mid-1960s Louis Frank showed that ions in the newly discovered plasma sheet had the energy spectral characteristics needed to explain the ring current's origin. The introduction of ion mass spectrometers on space missions during the 1970s revealed that O+ ions from the ionosphere contribute large fractions of the ring current's energy content. Precisely how cold O+ ions in the ionosphere are accelerated to ring-current energies still challenges scientific understanding.

Side Chain Influence on Main Chain Orientation of PPV-Type Oligomers

1999 ◽  
Vol 598 ◽  
Author(s):  
Ruth Müllner ◽  
Laurence Noirez ◽  
Egbert Zojer ◽  
Franz Stelzer ◽  
Günther Leising
Keyword(s):  
Magnetic Field ◽  
Neutron Diffraction ◽  
Main Chain ◽  
Side Chain ◽  
Phenylene Vinylene ◽  
Spectroscopic Methods ◽  
Polarized Optical Microscopy ◽  
Chain Orientation ◽  
H Nmr ◽  
Ft Ir

ABSTRACTOligo (p-phenylene vinylene)s OPV were synthesized having cyanobiphenyloxy-groups bonded to the vinylene double bonds via alkylene spacers. A Pd(0)-reaction was used to synthesize the oligomers starting with the dibromo-substituted benzene and the alkenyloxy-biphenyl-nitrile. The orientation of the mesogens by a magnetic field and their influence on the orientation of the main chain was investigated by means of neutron diffraction ND. Data on the photophysics of the oligomers were gained using several spectroscopic methods such as UV/VIS, polarized optical microscopy POM, SEC, 1H-NMR, FT-IR.

Ionlzation of fast hydrogen atoms in a strong magnetic field

1965 ◽  
Vol 5 (1) ◽  
pp. 85-86 ◽  
Author(s):  
E. S. Bohovik ◽  
F. I. Busol ◽  
V. A. Kovalenko ◽  
E. U. Skibenko ◽  
V. B. Yuferov
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
Hydrogen Atoms

Propagation properties of foreshock cavitons and spontaneous hot flow anomalies: Statistical results from a global hybrid-Vlasov simulation

2021 ◽  
Author(s):  
Vertti Tarvus ◽  
Lucile Turc ◽  
Markus Battarbee ◽  
Jonas Suni ◽  
Xóchitl Blanco-Cano ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Rest Frame ◽  
Low Frequency ◽  
Propagation Speed ◽  
Bow Shock ◽  
Linear Interaction ◽  
Frame Motion ◽  
Suprathermal Ions ◽  
Propagation Properties

<p>Foreshock cavitons are transient structures forming in Earth's foreshock as a result of non-linear interaction of ultra-low frequency waves. Cavitons are characterised by simultaneous density and magnetic field depressions with sizes of the order of 1 Earth radius. These transients are advected by the solar wind towards the bow shock, where they may accumulate shock-reflected suprathermal ions and become spontaneous hot flow anomalies (SHFAs), which are characterised by an enhanced temperature and a perturbed bulk flow inside them.<br>    Both spacecraft measurements and hybrid simulations have shown that while cavitons and SHFAs are carried towards the bow shock by the solar wind, their motion in the solar wind rest frame is directed upstream. In this work, we have made a statistical analysis of the propagation properties of cavitons and SHFAs using Vlasiator, a hybrid-Vlasov simulation model. In agreement with previous studies, we find the transients propagating upstream in the solar wind rest frame. Our results show that the solar wind rest frame motion of cavitons is aligned with the direction of the interplanetary magnetic field, while the motion of SHFAs deviates from this direction. We find that SHFAs have a faster solar wind rest frame propagation speed than cavitons, which is due to an increase in the sound speed near the bow shock, affecting the speed of the waves in the foreshock.</p>

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