Excitation and polarization analysis of the OD fragment radiation produced by dissociative electron impact on D2O

1982 ◽  
Vol 60 (8) ◽  
pp. 1168-1175 ◽  
Author(s):  
Kurt Becker ◽  
Günther Schulz
Keyword(s):  
Electron Impact ◽  
Time Scale ◽  
The Other ◽  
Polarization Analysis ◽  
Rotational Period ◽  
Dissociation Process ◽  
Parent Molecule ◽  
Dissociation Dynamics ◽  
Electronically Excited ◽  
Normal Water

The formation of electronically excited OD(A2Σ+) radicals following dissociative electron impact on D2O has been studied and a comparison with the H2O/OH (A2Σ+) dissociation system is made. Measurements of excitation functions reveal that the dissociation paths are largely unaffected by the deuteration of the parent molecule and even the weighting of the different dissociation channels leading to respectively slowly and rapidly rotating OD radicals is similar to the H2O dissociation process. On the other hand, the level of polarization of OD as compared with OH fragment radiation is found to be reduced by roughly a factor of 3. This may be explained in terms of an enhanced ratio of lifetime to rotational period for the parent D2O states. Thus the dissociation dynamics, i.e., the time scale between excitation and fragmentation, is demonstrated to react very sensitively when normal water is replaced by its deuterated specimen.

Dynamics of the KrF* Laser Multiphoton Dissociation of a Series of Arene Chromium Tricarbonyls

1988 ◽  
Vol 131 ◽  
Author(s):  
George W. Tyndall ◽  
Robert L. Jackson
Keyword(s):  
Gas Phase ◽  
Excited States ◽  
Dissociation Process ◽  
Parent Molecule ◽  
Electronically Excited ◽  
Arene Ligand ◽  
Multiphoton Dissociation ◽  
Sequential Absorption ◽  
The One ◽  
Direct Dissociation

ABSTRACTThe KrF* (248 nim) laser multiphoton dissociation (MPD) of a series of (arene)chromium tricarbonyls has been investigated in the gas-phase using emission spectroscopy to detect the excited state photoproducts. In the MPD of all compounds studied, chromium atoms are formed in a variety of electronically excited states via a two-channel dissociation mechanism. The predominant pathway for formation of the ground electronic state and the lowest excited states is by a sequential absorption/fragmentation process, where the product of the one-photon dissociation of the parent molecule absorbs an additional photon and dissociates to Cr(I). The higher energy Cr(I) states are formed exclusively by a direct dissociation process, where the parent absorbs multiple photons prior to dissociation. The distribution of excited chromium atoms formed in the direct channel is statistical for all compounds studied and is independent of the nature of the arene ligand. In contrast, the distribution of Cr(I) states formed via the sequential dissociation channel is strongly dependent on the vibrational density of states in the arene ligand.

scholarly journals Gas phase formation of c-SiC3molecules in the circumstellar envelope of carbon stars

2019 ◽  
Vol 116 (29) ◽  
pp. 14471-14478 ◽  
Author(s):  
Tao Yang ◽  
Luke Bertels ◽  
Beni B. Dangi ◽  
Xiaohu Li ◽  
Martin Head-Gordon ◽  
...  
Keyword(s):  
Carbon Star ◽  
Asymptotic Giant Branch ◽  
Formation Mechanisms ◽  
Circumstellar Envelope ◽  
Outer Envelope ◽  
Parent Molecule ◽  
Silicon Carbon ◽  
Electronically Excited ◽  
Circumstellar Environments ◽  
A Chain

Complex organosilicon molecules are ubiquitous in the circumstellar envelope of the asymptotic giant branch (AGB) star IRC+10216, but their formation mechanisms have remained largely elusive until now. These processes are of fundamental importance in initiating a chain of chemical reactions leading eventually to the formation of organosilicon molecules—among them key precursors to silicon carbide grains—in the circumstellar shell contributing critically to the galactic carbon and silicon budgets with up to 80% of the ejected materials infused into the interstellar medium. Here we demonstrate via a combined experimental, computational, and modeling study that distinct chemistries in the inner and outer envelope of a carbon star can lead to the synthesis of circumstellar silicon tricarbide (c-SiC3) as observed in the circumstellar envelope of IRC+10216. Bimolecular reactions of electronically excited silicon atoms (Si(1D)) with allene (H2CCCH2) and methylacetylene (CH3CCH) initiate the formation of SiC3H2molecules in the inner envelope. Driven by the stellar wind to the outer envelope, subsequent photodissociation of the SiC3H2parent operates the synthesis of the c-SiC3daughter species via dehydrogenation. The facile route to silicon tricarbide via a single neutral–neutral reaction to a hydrogenated parent molecule followed by photochemical processing of this transient to a bare silicon–carbon molecule presents evidence for a shift in currently accepted views of the circumstellar organosilicon chemistry, and provides an explanation for the previously elusive origin of circumstellar organosilicon molecules that can be synthesized in carbon-rich, circumstellar environments.

scholarly journals MASS SPECTRA OF SOME FUROQUINOLINE ALKALOIDS

1965 ◽  
Vol 43 (9) ◽  
pp. 2516-2521 ◽  
Author(s):  
D. M. Clugston ◽  
D. B. Maclean
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
The Other ◽  
Methoxyl Group ◽  
Quinoline Ring

The mass spectra of six furoquinoline alkaloids have been recorded and mechanisms have been proposed for their fragmentation upon electron impact. Strong metastable peaks, present in all spectra, have aided in the interpretation of the fragmentation of these alkaloids. The three alkaloids with a methoxyl group in the 8-position of the quinoline ring may be differentiated from the other three by the presence of relatively intense peaks at M-1 and M-29.

Weak Coupling Strategy for Multi-Physics CFD Simulation in Engineering Problems

2011 ◽  
Author(s):  
Makoto Yamamoto ◽  
Masaya Suzuki
Keyword(s):  
Strong Coupling ◽  
Time Scale ◽  
Weak Coupling ◽  
Particle Deposition ◽  
Cfd Simulation ◽  
The Other ◽  
Cfd Simulations ◽  
Sand Erosion ◽  
Coupling Strategy ◽  
The Difference

Multi-Physics CFD Simulation will be one of key technologies in various engineering fields. There are two strategies to simulate a multi-physics phenomenon. One is “Strong Coupling”, and the other is “Weak Coupling”. Each can be employed, based on time-scales of physics embedded in a problem. That is, when a time-scale of one physics is nearly same as that of the other physics, we have to use Strong Coupling to take into account the interaction between two physics. On the other hand, when one time-scale is quite different from the other one, Weak Coupling can be applied. Considering the present computer performance, Strong Coupling is difficult to be used in engineering design processes now. Therefore, we are focusing on Weak Coupling, and it has been applied to a number of multi-physics CFD simulations in engineering. We have successfully simulated sand erosion, ice accretion, particle deposition, electro-chemical machining and so on, with using Weak Coupling method. In the present study, the difference between strong and weak couplings is briefly described, and two examples of our multi-physics CFD simulations are expressed. The numerical results indicate that Weak Coupling strategy is promising in a lot of multi-physics CFD simulations.

scholarly journals Tracers confirm downward mixing of Tyrrhenian Sea upper waters associated with the Eastern Mediterranean Transient

2010 ◽  
Vol 7 (4) ◽  
pp. 1533-1557
Author(s):  
W. Roether ◽  
J. E. Lupton
Keyword(s):  
Deep Water ◽  
Time Scale ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
The Other ◽  
Tyrrhenian Sea ◽  
Convective Mixing ◽  
Deep Waters ◽  
Major Process ◽  
Gibraltar Strait

Abstract. Observations of tritium and 3He in the Tyrrhenian Sea, 1987–2009, confirm the enhanced convective mixing of intermediate waters into the deep waters that has been noted and associated with the Eastern Mediterranean Transient in previous studies. Our evidence for the mixing rests on increasing tracer concentrations in the Tyrrhenian deep waters, accompanied by decreases in the upper waters, which are supplied from the Eastern Mediterranean. The downward transfer is particularly evident between 1987 and 1997. Later on, information partly rests on increasing tritium-3He ages; here we correct the observed 3He for contributions released from the ocean floor. The Tyrrhenian tracer distributions are fully compatible with data upstream of the Sicily Strait and in the Western Mediterranean. The tracer data show that mixing reached to the bottom and confirm a cyclonic nature of the deep water circulation in the Tyrrhenian. They furthermore indicate that horizontal homogenization of the deep waters occurs on a time scale of several years. Various features point to a reduced impact of Western Mediterranean Deep Water (WMDW) in the Tyrrhenian during the enhanced-convection period. This is an important finding because it implies less upward mixing of WMDW, which has been named a major process to enable the WMDW to leave the Mediterranean via the Gibraltar Strait. On the other hand, the TDW outflow for several years represented a major influx of enhanced salinity and density waters into the deep-water range of the Western Mediterranean.

scholarly journals Magnetic Angle Changer for Studies of Electronically Excited Long-Living Atomic States

Atoms ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 71
Author(s):  
Łukasz Kłosowski ◽  
Mariusz Piwiński
Keyword(s):  
Magnetic Field ◽  
Numerical Analysis ◽  
Electron Impact ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Electronically Excited ◽  
Atomic States

A new geometry of a magnetic angle changer (MAC) device is proposed, which allows experiments to be run on electron impact excitation of long-lived states of target atoms. The details of the device’s design are presented and discussed together with a numerical analysis of its magnetic field.

The Conquest That Never Was: Ghana and the Almoravids, 1076. II. The Local Oral Sources

1983 ◽  
Vol 10 ◽  
pp. 53-78 ◽  
Author(s):  
David C. Conrad ◽  
Humphrey J. Fisher
Keyword(s):  
Time Scale ◽  
Oral Tradition ◽  
Eleventh Century ◽  
The Other ◽  
Oral Traditions ◽  
Positive Identification ◽  
The Subject ◽  
Oral Evidence ◽  
Remote Past ◽  
Written Sources

“The land took the name of the wells, the wells that had no bottom.”In Part I of this paper we examined the external written sources and found no unambiguous evidence that an Almoravid conquest of ancient Ghana ever occurred. The local oral evidence reviewed in this part of our study supports our earlier hypothesis, in that we find nothing in the traditions to indicate any conquest of the eleventh-century sahelian state known to Arab geographers as “Ghana.” Instead, the oral traditions emphasize drought as having had much to do with the eventual disintegration of the Soninke state known locally as “Wagadu.”An immediate problem involved in sifting the oral sources for evidence of an Almoravid conquest is that a positive identification between the Wagadu of oral tradition and the Ghana of written sources has never been established. Early observers like Tautain (1887) entertained no doubts in this regard, and recently Meillassoux seems to have accepted a connection, if not an identification, between Ghana and Wagadu when he notes that “les Wago, dont le nom a donné Wagadu, sont les plus clairement associés à l'histoire du Ghana.” However, much continues to be written on the subject, and the question remains a thorny one. On the lips of griots (traditional bards) and other local informants, Wagadu is a timeless concept, so a reliable temporal connection between people and events in the oral sources on one hand and Ghana at the time of the Almoravids on the other, is particularly elusive. Indeed, any link between the traditions discussed here and a specific date like 1076 must be regarded as very tenuous, as must any association of legendary events with Islamic dates. In western Sudanic tradition influenced by Islam, the hijra (A.D. 622) is both prestigious and convenient, a date with which virtually any event in the remote past can be associated, though such a claim may have nothing to do with any useful time scale.

scholarly journals On the survivability of planets in young massive clusters and its implication of planet orbital architectures in globular clusters

2019 ◽  
Vol 489 (3) ◽  
pp. 4311-4321 ◽  
Author(s):  
Maxwell X Cai ◽  
S Portegies Zwart ◽  
M B N Kouwenhoven ◽  
Rainer Spurzem
Keyword(s):  
Globular Cluster ◽  
Time Scale ◽  
Globular Clusters ◽  
Semimajor Axis ◽  
Stellar System ◽  
Dynamical Evolution ◽  
The Other ◽  
Crossing Time ◽  
Massive Clusters ◽  
Full Investigation

ABSTRACT As of 2019 August, among the more than 4000 confirmed exoplanets, only one has been detected in a globular cluster (GC) M4. The scarce of exoplanet detections motivates us to employ direct N-body simulations to investigate the dynamical stability of planets in young massive clusters (YMC), which are potentially the progenitors of GCs. In an N = 128 k cluster of virial radius 1.7 pc (comparable to Westerlund-1), our simulations show that most wide-orbit planets (a ≥ 20 au) will be ejected within a time-scale of 10 Myr. Interestingly, more than $70{{\ \rm per\ cent}}$ of planets with a < 5 au survive in the 100 Myr simulations. Ignoring planet–planet scattering and tidal damping, the survivability at t Myr as a function of initial semimajor axis a0 in au in such a YMC can be described as fsurv(a0, t) = −0.33log10(a0)(1 − e−0.0482t) + 1. Upon ejection, about $28.8{{\ \rm per\ cent}}$ of free-floating planets (FFPs) have sufficient speeds to escape from the host cluster at a crossing time-scale. The other FFPs will remain bound to the cluster potential, but the subsequent dynamical evolution of the stellar system can result in the delayed ejection of FFPs from the host cluster. Although a full investigation of planet population in GCs requires extending the simulations to multiGyr, our results suggest that wide-orbit planets and free-floating planets are unlikely to be found in GCs.

Decisions and the Uncertainty of Behaviour

Behaviour ◽  
1973 ◽  
Vol 45 (1-2) ◽  
pp. 83-103 ◽  
Author(s):  
◽  
Marian Dawkins
Keyword(s):  
Time Scale ◽  
The Other ◽  
Drinking Behaviour ◽  
Temporal Patterning ◽  
Domestic Chicks ◽  
Decision Structure ◽  
Videotape Analysis ◽  
Behavioural Sequence ◽  
Different Parts ◽  
Over Time

AbstractBehaviour can be described in terms of its changing uncertainty or decision structure over time. Such a description is economical, maximally informative and may well be of importance neurophysiologically. We try to show that the methods which are normally used to detect temporal patterning between already recognized behavioural acts can also be used on a finer time scale to detect moment to moment patterns of posture within those acts. From such analyses, it is possible to calculate the 'decisioniness' or 'uncertainty' of different parts of the behavioural sequence. We illustrate this by an attempt to describe the decision structure of the drinking behaviour of domestic chicks, using frame by frame videotape analysis. For example, it appears that the first downstroke phase of each drink is more uncertain as to outcome than the other phases, suggesting that 'decisions' are taken during the downstroke. We end with an attempt to plot a continuous graph of behaviour uncertainty against time sampled at 50 msec intervals.

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