A time‐of‐flight spectrometer for the measurement of angular distributions of scattered slow positrons and electrons

1980 ◽  
Vol 51 (7) ◽  
pp. 935-943 ◽  
Author(s):  
P. G. Coleman ◽  
J. D. McNutt ◽  
J. T. Hutton ◽  
L. M. Diana ◽  
J. L. Fry
Keyword(s):  
Time Of Flight ◽  
Angular Distributions

Nanosecond and Femtosecond UV Laser Ablation of CdTe (100): Time-Of-Flight and Angular Distributions

1993 ◽  
Vol 334 ◽  
Author(s):  
P.D. Brewer ◽  
M. Späth ◽  
M. Stuke
Keyword(s):  
Laser Ablation ◽  
High Resolution ◽  
Mass Spectrometer ◽  
Multiphoton Ionization ◽  
Time Of Flight ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Dye Laser ◽  
Angular Distributions ◽  
Uv Laser

AbstractAngularly resolved time-of-flight (TOF) measurements have been used to probe the velocity and angular distributions of Cd atoms and Te2 molecules ejected from CdTe (100) substrates under irradiation by 248 nm nanosecond and sub-picosecond laser pulses. These experiments employ a dye laser TOF mass spectrometer with resonance enhanced multiphoton ionization for sensitive, high resolution detection of the desorbed products. The velocity distributions are well described by Maxwell-Boltzmann distributions for low fluence nanosecond (<60 mJ/cm2) and sub-picosecond (<3.3 mJ/cm2) pulses. Angular flux distributions for nanosecond irradiation are observed to be highly forward peaked about the surface normal, whereas, for sub-picosecond irradiation the distribution approaches cos3θ.

Spectroscopic Study of 32S Through the 31P(d,n)32S Reaction

1974 ◽  
Vol 52 (14) ◽  
pp. 1288-1294 ◽  
Author(s):  
A. H. Hussein ◽  
G. C. Neilson ◽  
W. J. McDonald ◽  
W. K. Dawson
Keyword(s):  
Spectroscopic Study ◽  
Shell Model ◽  
Cross Sections ◽  
Differential Cross ◽  
Time Of Flight ◽  
Angular Distributions ◽  
Absolute Differential ◽  
Spectroscopic Factors ◽  
Model Predictions ◽  
Theoretical Predictions

The 31P(d,n)32S reaction has been studied at deuteron energies of 4.0 and 5.45 MeV. Neutron energies were measured by time of flight. Absolute differential cross sections of seven levels in 32S have been measured and compared with the theoretical predictions of both the DWBA and compound statistical theories. Analysis of the angular distributions yielded lP values and absolute spectroscopic factors. These results have been compared with those from other experiments and shell model predictions.

Inelastic scattering of slow positrons by helium, neon, and argon atoms

1982 ◽  
Vol 60 (4) ◽  
pp. 584-590 ◽  
Author(s):  
P. G. Coleman ◽  
J. T. Hutton ◽  
D. R. Cook ◽  
C. A. Chandler
Keyword(s):  
Energy Loss ◽  
Inelastic Scattering ◽  
Multiple Scattering ◽  
Time Of Flight ◽  
Angular Distributions ◽  
Atomic Excitation ◽  
Helium Neon

Measurements of the excitation and ionization of helium, neon, and argon by positrons of energies between threshold and 50 eV, utilising time-of-flight energy loss spectrometry, are reported. Scattering into forward angles up to 60° is observed and the measurements suggest that sharp forward lobes exist in the angular distributions of positrons scattered following atomic excitation. Multiple scattering corrections to the measurements are described. Comparison is made with the inelastic scattering of electrons by the same atoms, and connections drawn between the present results and those of the recent complementary studies of Griffith et al. and Charlton et al.

Measurements of Neutron Polarizations for Deuteron Energies from 0.87 to 5.00 MeV

1972 ◽  
Vol 50 (8) ◽  
pp. 783-790 ◽  
Author(s):  
J. R. Smith ◽  
S. T. Thornton
Keyword(s):  
Energy Range ◽  
Liquid Helium ◽  
Legendre Polynomial ◽  
Measurement Techniques ◽  
Time Of Flight ◽  
Angular Distributions ◽  
Contour Maps ◽  
Neutron Time ◽  
Polarized Neutron ◽  
Polynomial Expansions

Neutron time-of-flight techniques have been used to measure [Formula: see text] polarization angular distributions for several deuteron energies from 0.87 to 5.00 MeV. Liquid helium served as the polarized neutron analyzer. From Legendre polynomial expansions of σ(Θ) and P(Θ)σ(Θ), contour maps of P(Θ) and P2(Θ)σ(Θ) have been produced for the energy range 0.87 to 5.00 MeV. Comparison with previous results and measurement techniques are discussed. Nucleon polarizations from the charge symmetric reactions [Formula: see text] and [Formula: see text] are compared.

Threshold Photoneutron Angular Distributions and an M1 Giant Resonance in 208Pb

1975 ◽  
Vol 53 (15) ◽  
pp. 1422-1433 ◽  
Author(s):  
L. C. Haacke ◽  
K. G. McNeill
Keyword(s):  
Giant Resonance ◽  
Time Of Flight ◽  
Angular Distributions ◽  
Neutron Shell ◽  
Spin Flip ◽  
Proton Shell

Threshold photoneutron time-of-flight spectra from the 208Pb(γ,n)207Pb reaction have been measured at five angles to the incident photons. Angular distributions obtained for 14 resonances within 850 keV of the 208Pb(γ,n) threshold have led to assignments of M1 strength totalling 67.5 ± 12 eV. The total M1 strength available from spin-flip transitions from the i13/2 neutron shell and the h11/2 proton shell has been calculated to be 100 eV (Weiss). Thus, the data confirm the existence of an M1 giant resonance just above threshold in 208Pb.

Angle Resolved Time-of-Flight Measurements of the Excimer Laser Induced Etching of Silicon in a Chlorine Environment

1988 ◽  
Vol 129 ◽  
Author(s):  
T.S. Baller ◽  
J. van Zwol ◽  
S.T. de Zwart ◽  
G.N.A. van Veen ◽  
H. Fell ◽  
...  
Keyword(s):  
Gas Phase ◽  
Excimer Laser ◽  
Time Of Flight ◽  
Laser Pulses ◽  
Angular Distributions ◽  
Desorption Process ◽  
Surface Time ◽  
The Mean ◽  
Laser Induced Etching ◽  
Flight Measurements

ABSTRACTSi (100) samples have been irradiated with excimer laser pulses (λ = 308nm, pulsewidth =28ns) in a low pressure chlorine environment, at a fluence just enough to melt the surface. Time-of-flight spectra of the particles desorbed due to the laser irradiation have been measured as a function of effective chlorine pressure and desorption angle. Maxwell- Boltzmann distributions have been used to fit the measurements. The mean kinetic energy per particle increases with increasing chlorine pressure. Angular distributions of the desorbed particles are found to be cosine like at a chlorine coverage much less than a monolayer and sharply peaked along the surface normal at coverages on the order of a monolayer. Monte-Carlo simulations of the desorption process show that due to collisions between the desorbed particles the change in angular distribution can be explained. The increase in mean energy with increasing chlorine coverage however cannot be explained by gas phase collisions. A possible desorption process is suggested.

Applications of Time-OF-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)

1990 ◽  
Vol 48 (2) ◽  
pp. 308-309
Author(s):  
Bruno Schueler ◽  
Robert W. Odom
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Structural Information ◽  
Time Of Flight ◽  
Biological Tissues ◽  
Polymer Surfaces ◽  
Tof Sims ◽  
Secondary Ions ◽  
Ion Mass Spectrometry ◽  
Secondary Ion

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) provides unique capabilities for elemental and molecular compositional analysis of a wide variety of surfaces. This relatively new technique is finding increasing applications in analyses concerned with determining the chemical composition of various polymer surfaces, identifying the composition of organic and inorganic residues on surfaces and the localization of molecular or structurally significant secondary ions signals from biological tissues. TOF-SIMS analyses are typically performed under low primary ion dose (static SIMS) conditions and hence the secondary ions formed often contain significant structural information.This paper will present an overview of current TOF-SIMS instrumentation with particular emphasis on the stigmatic imaging ion microscope developed in the authors’ laboratory. This discussion will be followed by a presentation of several useful applications of the technique for the characterization of polymer surfaces and biological tissues specimens. Particular attention in these applications will focus on how the analytical problem impacts the performance requirements of the mass spectrometer and vice-versa.

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