This thesis presents the results of the research of several higher levels of F 18 with the help of 0 17( p, a )N14 of IS achievement. Several angular momentum and parity properties were investigated with N14. This relationship is important in light of a recent paper by Fowler, Greenstein and Hoyle (1961) discussing the formation of elements in the early history of the solar system.
A Kellogg Laboratory 2-Mv electrostatic generator was used to accelerate protons for this experimental determination. The signal taken from the horizontal slots at the bottom of the analyzer was used to regulate the generator voltage. The other end of the lucite was sealed to the Dumont 6291 photomultiplier surface in the same manner.
The midpoint of the step in the coarse target gamma ray yield was observed to occur at a setting of V :: 0.8686 decivolts. The bombardment energy is known from the calibration of the electrostatic analyzer, and the energy of protons elastically scattering from the Cu atoms on the target surface can be calculated from the kinematics.
TARGETS A. Preparation
The oxide was found to be stable - no oxygen loss was detectable with the beam currents of the order of 1 "microamp or less and the beam spot size of the order of 1 mm x 2 mm used in this experiment. It is therefore important to to know which fraction of the nickel atoms in the target has been oxidized. From the profile, both the degree of oxidation of the nickel and the thickness of the oxide layer can be determined.
The decrease in counts at the step in the oxidized target is due to the influence of the stopping power of the oxygen. 1 is the ratio of the scattered energy to the incident energy as determined from kinematics (Brown, 1951). The number and distribution of 0 17 atoms in the target was a function of the target spot bombarded.
Although the yield was lower for nickel oxide targets, most of the data was obtained with these targets. Thus, the magnet setting determines the number of target atoms per cm as long as it is set to detect only 2 particles that are completely produced in the uniformly oxidized region of the target.
EXPERIMENTAL PROCEDURE A. Nickel Oxide Target Data
Due to the low yield of alpha particles in this experiment, both the entrance and exit slits of the spectrometer were removed. By removing the entrance holes, the full solid angle of the spectrometer could be used. When recording the data, the entrance slits of the target chamber were first adjusted so that the proton beam hit the target surface in the center of the target chamber.
It was easy to adjust the gain of the pulse amplifier and the bias voltage of the amplifier so that the peak of the pulse height. An example of the raw data taken at the 672 kev resonance is shown in Figure. The highest count rate was observed at the peak of the broad resonance of 1274 kev and was 630 counts per integration.
When taking the 017(p,a)N14 . data with this nickel oxide focus on the effect of the alpha particles from the 0 18 . was only observable when attempting to measure quite low, non-resonant cross-sections. Due to the length of the runs required in the case of the two lowest measured cross sections (at bombardment energies 804 and 854 kev) it was not possible to collect all data at the same target location.
ANALYSIS OF EXPERIMENTAL DATA
The quantities £ 1 and £ 2 are the stop cross sections in the target material for the incoming and outgoing particles, respectively. The proton energy ElM corresponding to the midpoint on the leading edge of the target profile at. the beginning of the run and the target thickness £t in energy units can be found from the reference profile using Eq. original carbon thickness £c is then. L results in an error of 10%, which must be compared with the statistical error to give the error in the absolute cross section.
Thus, an error of 10'70 was assumed in the values used for the alpha particle stopping cross section in nickel oxide. The resonance energies and widths were found to be. where the errors are estimated from the analysis and do not include energy scale errors as discussed in Section V-B. The energy scale errors, however, are included in Table VII, which gives a summary of all the level parameters as determined in this experiment. In Appendix D, a formula is derived for the laboratory yield of alpha particles Y L (E , lB) as a function of the proton bombardment energy EIB for the case of a very narrow (6-functional) cross section resonance.
There is a discrepancy between the calculated curves and the experimental data, which appears on the wings of the yield curves. We can then calculate the quantity f3g r r I r v. system with the following formula.
THE ASTROPHYSICAL PROBLEM A. General Discussion
The observation of very narrow levels at low energy in this experiment leads to the assumption that these levels will have very little effect at energies of interest for stellar reactions. To obtain the section factor, an estimate of the dimensionless reduced widths e2 and e2 for. We will now give rough estimates for the 9292 product based on current experience.
Analysis of the remaining narrow levels would involve unwarranted guesses for the orbital angular momentum 1. Based on the order of magnitude it follows from the previous rough analysis, the value It is thought that (c) is unlikely and that the best estimate of the processing temperature is about 17 million degrees.
Here, Zlc and ZOc are the numbers of charges of the two particles of the c pair. The energy dependence of the cross section of the factors and the only residuals of the scattering matrix in the angular distribution function are the amplitudes for the formation of states through the various spins of the channel, which are included in the. We then discuss the problem of interpreting the area under the yield curve.
The present notation differs from that of Bardin (1961) in that he uses EZO to refer to the total energy of the emerging particles. ZS on the energy reception 6 E = ZE / R of the spectrometer (we assume a rectangular dis- .. tribut for the energy reception of the spectrometer) gives the laboratory yield Y L{E. Here Ern is the energy setting of the spectrometer and R = p/Ap is the momentum resolution of the spectrometer.
We prefer here not to use X as a variable, but to suffer the safe depth to the target by the energy loss in . We further discuss the problem of the relationship of the area ay under the yield curve with the level parameter s. The situation then reduces to that considered by Gove (1959) in which he shows that the area is independent of the energy spread in the beam or the barrier of internal particles s.
We let Ll.Ep and Ll.EO' stand for the hard widths of protons and alpha particles respectively. The factor 2.35 is the ratio of the full width at half maximum to the rms deviation for a Gaussian.
P channel, E being the proton energy in the laboratory
6 TARGET BACK
The error bars are omitted from the data obtained when the back of the target was bombarded.
560 FIG.?
The solid histogram is for the front of the target and the dashed histogram is for the rear of the target. The experimental resolution was about 5 kev due to spectrometer resolution and straggling, and the data in this figure have not been corrected for this resolution.
LAB =150 0
520 FIG . 12
8 LAS =150°
PROTON BOMBARDING ENERG~LAB
925 FIG . 16
34; III
61RON OXIDE TARGET
NICKEL OXIDE TARGET
Error bars show statistical errors only, and the absolute scale of the cross section is accurate to 10"10.
N III I
The points are taken from Tables II and III, and the dashed curves are polynomials fitted to these points. An example of both constructive interference and destructive interference between levels is shown. This curve is for the constructive interference between the two levels contributing to the star cross section.
This curve is for destructive interference between the two planes contributing to the star cross section. This curve is for constructive interference between the two planes contributing to the star cross section.
CONS