scholarly journals The Dynamic Collective Model Interpretation of the Photoneutron Cross Section of 181Ta

1973 ◽  
Vol 26 (5) ◽  
pp. 585 ◽  
Author(s):  
RS Hicks ◽  
BM Spicer
Keyword(s):  
Fine Structure ◽  
Excitation Energy ◽  
Cross Section ◽  
Neutron Detection ◽  
Collective Model ◽  
High Excitation ◽  
Absolute Value ◽  
Model Interpretation ◽  
Quadrupole Resonance ◽  
The Cross

The cross section for photoneutron production in 181Ta has been measured from threshold to 28� 8 MeV using bremsstrahlung and direct neutron detection. Integrated between these limits, the absolute value of the cross section has been determined to be 2 '47 �O' 35 MeV. b. An examination of the cross section variation with excitation energy reveals the existence of the giant quadrupole resonance lying on the high excitation edge of the dipole peak. This provides additional evidence for the validity of the dynamic collective model. The present data do not support the existence of extensive fine structure below 17 MeV, as proposed by Ishkhanov et al. (1969).

scholarly journals Fine structure of plastids during androgenesis in Hordeum vulgare L.

2014 ◽  
Vol 49 (3) ◽  
pp. 205-210 ◽  
Author(s):  
Fortunat Młodzianowski ◽  
Krystyna Idzikowska
Keyword(s):  
Fine Structure ◽  
Hordeum Vulgare ◽  
Cross Section ◽  
Egg Cell ◽  
Hordeum Vulgare L ◽  
Starch Grains ◽  
Ultrathin Sections ◽  
The Cross ◽  
Plastid Ribosomes ◽  
Fertilized Egg

The fine structure of plastids was studied in the course of androgenesis in in the pollen of <em>Hordeum vulgare</em> L. It was found that these organelles occur in all stages of androgenesis. Their structure was simple and was frequently manifested on the cross section only by the presence of the envelope and matrix of different degree of density. Single thylakoids, nucleoid-like regions and starch grains were, however, also noted. The structure of plastids in embryoids formed from microspores of barley was compared with embryos developed from fertilized egg cell, and we did not found any fundamental differences between them. However, only plastid ribosomes were difficult to identify on ultrathin sections in embryoids and in the embryos.

UPS of a-Si:H: What is the energy of the Er 4f states?

2000 ◽  
Vol 609 ◽  
Author(s):  
Leandro R. Tessler ◽  
Cínthia Piamonteze ◽  
Ana Carola Iniguez ◽  
Abner de Siervo ◽  
Richard Landers ◽  
...  
Keyword(s):  
Binding Energy ◽  
Excitation Energy ◽  
Cross Section ◽  
Energy Gap ◽  
Valence States ◽  
Erbium Doped ◽  
Order Of Magnitude ◽  
Synchrotron Light ◽  
The Cross ◽  
Er Doped

ABSTRACTOne very important problem concerning erbium-doped silicon is the electronic structure of the Er3+ impurities. In particular, it is still not clear if the 4f levels can be treated as frozen core levels or their overlap with s and p states of their neighbors must be considered explicitly. For crystalline Si, the 4f levels have been supposed to be anywhere between 20 eV below the valence band and within the energy gap. In this paper we report on the first ultraviolet photoemission spectroscopy (UPS) measurements on Er-doped a-Si:H. Samples of a-Si:H<Er> with different Er contents (up to 1 at. % Er) were prepared by co-sputtering from a Si target partially covered with metallic Er platelets. In order to enhance the Er states relative to the Si and H states, the excitation energy was tuned between 40 and 140 eV with a synchrotron light source. At 140 eV excitation energy the cross-section of the Er 4f and 5p states is more than an order of magnitude higher than the cross section of the Si 3s or 3p states. As the Er concentration increases, a shoulder and then a peak appears at 10.0±0.5 eV binding energy. The intensity and width of this peak is well correlated with the Er concentration, and with the Er 5p and 5p½ levels at 26 and 32 eV binding energy, respectively. We attribute the peak at 10.0±0.5 eV binding energy to the Er 4f level. These are the only occupied states that can be related to the presence of Er, indicating that these levels are not valence states and consequently can be treated as frozen core levels.

Theory of excitation transfer in collisions between alkali atoms. I. Identical partners

1969 ◽  
Vol 47 (12) ◽  
pp. 1237-1248 ◽  
Author(s):  
E. I. Dashevskaya ◽  
A. I. Voronin ◽  
E. E. Nikitin
Keyword(s):  
Excitation Energy ◽  
Excited States ◽  
Cross Section ◽  
Electronic Excitation ◽  
Electronic States ◽  
Excitation Transfer ◽  
Electronic Excitation Energy ◽  
Alkali Atoms ◽  
The Cross

A mechanism is derived for nonresonant transfer of electronic excitation energy, induced in the process M*(2P3/2) + M(2S1/2) → M*(2P1/2) + M(2S1/2), where M and M* are identical alkali atoms in the ground and first excited states, respectively. Various types of interactions, responsible for the nonadiabatic combination of electronic states of the quasi molecule M2*, were considered, and their respective contributions to the cross section for excitation transfer were determined.

scholarly journals Δ-Isobar contribution to the pion production in the reaction pp → {pp}sπ0

2019 ◽  
Vol 204 ◽  
pp. 01015
Author(s):  
Yuriy Uzikov
Keyword(s):  
Excitation Energy ◽  
Cross Section ◽  
Pion Production ◽  
Forward Direction ◽  
Dominant Contribution ◽  
Final State ◽  
Proton Pair ◽  
Order Of Magnitude ◽  
The Cross ◽  
The One

ANKE@COSY data on the cross section of the reaction pp → {pp}sπ0, where {pp}s is the proton pair in the 1S 0 state at small excitation energy Epp = 0 – 3 MeV, obtained at beam energies 0.5 - 2.0 GeV are analyzed within the one-pion exchange model. The model involves the subprocess π0 p → π0 p and accounts for the final state pp-interaction. A broad maximum observed in the cross section of the reaction pp → {pp}sπ0 at 0.5 - 1.4 GeV in the forward direction is explained by this model as a dominant contribution of the isospin $\cfrac{3}{2}$ in the π0 p-scattering. The second bump in data at 2 GeV is underpredicted within this model by one order of magnitude. An explicit excitation of the Δ(1232)-isobar using the box-diagram is also considered in the region of the first maximum.

Fine structure of the cross section of contact inelastic scattering of an X-ray photon by an atom

2008 ◽  
Vol 105 (1) ◽  
pp. 1-6
Author(s):  
A. N. Khoperskiĭ ◽  
A. M. Nadolinskiĭ ◽  
A. S. Kasprzhitskiĭ
Keyword(s):  
Fine Structure ◽  
Inelastic Scattering ◽  
Cross Section ◽  
X Ray ◽  
The Cross

Sensitized Fluorescence in Cadmium Induced in Collisions with Excited Hg Atoms

1974 ◽  
Vol 52 (22) ◽  
pp. 2228-2234 ◽  
Author(s):  
M. Czajkowski ◽  
L. Krause
Keyword(s):  
Excitation Energy ◽  
Cross Section ◽  
Ground State ◽  
Inelastic Collisions ◽  
Low Density ◽  
Resonance Fluorescence ◽  
Vapor Mixture ◽  
Sensitized Fluorescence ◽  
Fluorescence Measurements ◽  
The Cross

The transfer of excitation energy induced in inelastic collisions between excited Hg atoms and ground-state Cd atoms was studied using methods of sensitized fluorescence. Hg atoms in a low-density Hg–Cd vapor mixture were excited with Hg 2537 Å resonance radiation to the 63P1 state and interacted with the Cd atoms which became collisionally excited to the 53P1 state and subsequently decayed emitting sensitized fluorescence. Measurements of relative intensities of Hg 2537 Å resonance fluorescence and Cd 3261 Å sensitized fluorescence yielded the cross section Q(63P1 → 53P1) = 4.6 × 10−2 Å2. The efficiency of the excitation transfer was enhanced by the addition of small quantities of N2 to the Hg–Cd system. The cross section for quenching of the Cd 53P1 state by collisions with N2 was found to be 1.7 Å2.

scholarly journals The Cross Section for the 16O(g,n)15O Reaction

1957 ◽  
Vol 10 (2) ◽  
pp. 326 ◽  
Author(s):  
BM Spicer
Keyword(s):  
Fine Structure ◽  
Cross Section ◽  
Present Note ◽  
Yield Curve ◽  
Giant Resonance ◽  
Yield Curves ◽  
Single Level ◽  
The Cross

There have been a number of attempts to account for the nature of the giant resonance of nuclear photodisintegration (e.g. Goldhaber and Teller 1948; Steinwedel and Jensen 1950; Wilkinson 1955; and others). Levinger and Bethe (1950) believe that a " many-level" theory of the giant resonance is more satisfactory than a single-level theory. The existence of fine structure in the yield curve of the 16O(?,11,) reaction at energies near the giant resonance (Penfold and Spicer 1955) supports this conclusion. The purpose of the present note is to show that the existence of structure within the giant resonance may be demonstrated more simply than by the tedious study of fine structure in yield curves.

CALCULATION OF BREAKUP CROSS SECTION FOR FOUR-BODY BREAKUP REACTION SYSTEMS

2010 ◽  
Vol 25 (21n23) ◽  
pp. 1903-1906
Author(s):  
TAKUMA MATSUMOTO ◽  
KIYOSHI KATŌ ◽  
MASANOBU YAHIRO
Keyword(s):  
Excitation Energy ◽  
Cross Section ◽  
Cross Sections ◽  
Breakup Reaction ◽  
New Method ◽  
Breakup Cross Section ◽  
Reaction Systems ◽  
Coupled Channels ◽  
The Cross

We present a new method of smoothing discrete breakup cross sections calculated by the method of continuum-discretized coupled-channels. In the four-body breakup reaction of 12 C (6 He , nn4 He ) at E in = 229.8 MeV , the continuous breakup cross section is evaluated as a function of the excitation energy of 6 He . Convergence of the cross section with respect to extending the modelspace is also confirmed.

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