| 1. |
- Acharya, B. S., et al.
(författare)
-
Introducing the CTA concept
- 2013
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 43, s. 3-18
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. (C) 2013 Elsevier B.V. All rights reserved.
|
|
| 2. |
|
|
| 3. |
- Dahl-Jensen, D., et al.
(författare)
-
Eemian interglacial reconstructed from a Greenland folded ice core
- 2013
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 493:7433, s. 489-494
-
Tidskriftsartikel (refereegranskat)abstract
- Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 +/- 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 +/- 250 metres, reaching surface elevations 122,000 years ago of 130 +/- 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Chartkunchand, Kiattichart C., et al.
(författare)
-
Radiative lifetimes of the bound excited states of Pt-
- 2016
-
Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 94:3
-
Tidskriftsartikel (refereegranskat)abstract
- © 2016 American Physical Society.The intrinsic radiative lifetimes of the 5d106sS1/22 and 5d96s2 D3/22 bound excited states in the platinum anion Pt- have been studied at cryogenic temperatures at the Double ElectroStatic Ion Ring Experiment (DESIREE) facility at Stockholm University. The intrinsic lifetime of the higher-lying 5d106s S1/22 state was measured to be 2.54±0.10s, while only a lifetime in the range of 50-200 ms could be estimated for the 5d96s2 D3/22 fine-structure level. The storage lifetime of the Pt- ion beam was measured to be a little over 15 min at a ring temperature of 13K. The present study reports the lifetime of an atomic negative ion in an excited bound state with an electron configuration different from that of the ground state.
|
|
| 7. |
- Kamińska, Magdalena, et al.
(författare)
-
Lifetime of the bound excited level in Ni
- 2016
-
Ingår i: Physical Review A. - 1050-2947 .- 1094-1622. ; 93:1
-
Tidskriftsartikel (refereegranskat)abstract
- The intrinsic lifetime of the upper level in the bound-bound 3d(9) 4s(2) D-2(3/2) -> 3d(9) 4s(2) D-2(5/2) radiative transition in Ni- was measured to be 15.1 +/- 0.4 s. The experiment was performed at cryogenic temperatures in one of the ion-beam storage rings of the Double ElectroStatic Ion Ring ExpEriment facility at Stockholm University. The storage lifetime of the Ni- ion beam was measured to be close to 5 min at a ring temperature of 13 K.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Anderson, Emma K., 1986-, et al.
(författare)
-
Fragmentation of and electron detachment from hot copper and silver dimer anions : A comparison
- 2023
-
Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 107:6
-
Tidskriftsartikel (refereegranskat)abstract
- We measured the spontaneous decays of internally hot copper and silver dimer anions, and , stored in one of the two ion-beam storage rings of the Double Electrostatic Ion Ring Experiment (DESIREE) at Stockholm University. A coincidence detection technique was utilized enabling essentially background-free measurements of -> Cu + Cu- and -> Ag + Ag- fragmentation rates. Furthermore, the total rates of neutral decay products (monomers and dimers) were measured and the relative contributions of fragmentation and electron emission ( -> Cu2 + e- and -> Ag2 + e-) were deduced as functions of storage time. Fragmentation is completely dominant at early times. However, after about 20 ms of storage, electron emission is observed and becomes the leading decay path after 100 ms for both dimer anions. The branching ratios between fragmentation and electron emission (vibrationally assisted autodetachment processes) are very nearly the same for and Ag-2 throughout the present storage cycle of 10 seconds. This is surprising considering the difference between the electron affinities of the neutral dimers, Cu2 and Ag2, and the difference between the and the dissociation energies.
|
|
