scholarly journals Hyperfine Interactions in Organic Fragments

2021 ◽  
Author(s):  
◽  
John Patrick Macarthur Bailey
Keyword(s):  
High Speed ◽  
Organic Molecules ◽  
Electronic Computer ◽  
Applied Mathematics ◽  
Hyperfine Interactions ◽  
Industrial Research ◽  
Molecular Orbital Calculations ◽  
Master Of Science ◽  
Alternative Approaches ◽  
Division Department

<p>This thesis, the first thesis in theoretical chemistry submitted for the degree of Master of Science at Victoria University of Wellington, has been designed to illustrate two alternative approaches to theoretical studies. The first five chapters illustrate the modern use of operator methods; the last two are concerned mainly with molecular orbital calculations for large organic molecules, using a giant high speed electronic computer. I am deeply indebted to Mr Keith Morris, of the Applied Mathematics Division, Department of Scientific and Industrial Research, for his generous and highly competent help in writing computing programs, and operating computers, at all odd hours of the day and night, for the calculations in this thesis. I would also like to thank Dr R.M. Golding, for useful discussions, and the Director, Applied Mathematics Division, Department of Scientific and Industrial Research, for making computing facilities available.</p>

scholarly journals Hyperfine Interactions in Organic Fragments

2021 ◽  
Author(s):  
◽  
John Patrick Macarthur Bailey
Keyword(s):  
High Speed ◽  
Organic Molecules ◽  
Electronic Computer ◽  
Applied Mathematics ◽  
Hyperfine Interactions ◽  
Industrial Research ◽  
Molecular Orbital Calculations ◽  
Master Of Science ◽  
Alternative Approaches ◽  
Division Department

<p>This thesis, the first thesis in theoretical chemistry submitted for the degree of Master of Science at Victoria University of Wellington, has been designed to illustrate two alternative approaches to theoretical studies. The first five chapters illustrate the modern use of operator methods; the last two are concerned mainly with molecular orbital calculations for large organic molecules, using a giant high speed electronic computer. I am deeply indebted to Mr Keith Morris, of the Applied Mathematics Division, Department of Scientific and Industrial Research, for his generous and highly competent help in writing computing programs, and operating computers, at all odd hours of the day and night, for the calculations in this thesis. I would also like to thank Dr R.M. Golding, for useful discussions, and the Director, Applied Mathematics Division, Department of Scientific and Industrial Research, for making computing facilities available.</p>

The use of a high-speed digital computer for the direct determination of crystal structures. I

1955 ◽  
Vol 227 (1171) ◽  
pp. 486-500 ◽  
Keyword(s):  
Crystal Structure ◽  
Fourier Series ◽  
Crystal Structures ◽  
Digital Computer ◽  
High Speed ◽  
Electronic Computer ◽  
Direct Determination ◽  
Direct Methods ◽  
Weighting Factor

A method is described whereby an electronic computer, the EDSAC, may be used to select a set, or sets, of signs for the coefficients F (h) of a Fourier series, such that the Fourier series, satisfies a certain condition. This condition is expressed as X ≡ Ʃ h Ʃ h ' P (h,h') S (h) S (h') S (h+h')≽ X 0 , where S (h) denotes the sign of F (h) and P (h, h') is a weighting factor related to the probability that S (h) S (h') = S (h+h'). In certain circumstances the determination of a crystal structure which is beyond the range of other direct methods is possible by this procedure.

The use of a high-speed digital computer for the direct determination of crystal structures. II

1957 ◽  
Vol 243 (1233) ◽  
pp. 281-288 ◽  
Keyword(s):  
High Speed ◽  
Electronic Computer ◽  
Direct Determination ◽  
Preceding Paper ◽  
Contour Maps ◽  
Unknown Structure ◽  
New Criterion ◽  
High Degree ◽  
Selection Of

This paper discusses some possible procedures for crystal structure determination using the X criterion developed in the preceding paper of the series. In that paper it was shown that, under favourable circumstances, the signs of the largest terms in the Fourier series representa­tion of ρ , the electron density in the unit cell, can be determined directly. The magnitudes of these terms can be found by experiment. In less favourable cases the correct set of signs, to a high degree of probability, lies among several hundred possible sets which can be determined by the processes described. A new criterion is proposed for selection of a lesser number, say a dozen, ‘most probable’ sets of signs. These latter sets can be tested by inspection of the corre­sponding contour maps of ρ . The new criterion has been successfully used in determining the unknown structure of nitroguanidine. Techniques for the selection of most probable sets and also for evaluation of ρ at suitable points in space using an electronic computer, the EDSAC, are described.

scholarly journals Organic Molecules: Is It Possible to Distinguish Aromatics from Aliphatics Collected by Space Missions in High-Speed Impacts?

Sci ◽  
2020 ◽  
Vol 2 (2) ◽  
pp. 41
Author(s):  
Mark Burchell ◽  
Kathryn Harriss
Keyword(s):  
High Speed ◽  
Organic Molecules ◽  
Chemical Structures ◽  
Surface Ocean ◽  
Life Itself ◽  
Organic Particles ◽  
Open Question ◽  
The Impact ◽  
The Relationship ◽  
Complex Organic

A prime site of astrobiological interest within the Solar System is the interior ocean of Enceladus. This ocean has already been shown to contain organic molecules, and is thought to have the conditions necessary for more complex organic biomolecules to emerge and potentially even life itself. This sub-surface ocean has been accessed by Cassini, an unmanned spacecraft that interacted with the water plumes ejected naturally from Enceladus. The encounter speed with these plumes and their contents, was between 5 and 15 km s−1. Encounters at such speeds allow analysis of vapourised material from submicron-sized particles within the plume, but sampling micron-sized particles remains an open question. The latter particles can impact metal targets exposed on the exterior of future spacecraft, producing impact craters lined with impactor residue, which can then be analysed. Although there is considerable literature on how mineral grains behave in such high-speed impacts, and also on the relationship between the crater residue and the original grain composition, far less is known regarding the behaviour of organic particles. Here we consider a deceptively simple yet fundamental scientific question: for impacts at speeds of around 5–6 kms−1 would the impactor residue alone be sufficient to enable us to recognise the signature conferred by organic particles? Furthermore, would it be possible to identify the organic molecules involved, or at least distinguish between aromatic and aliphatic chemical structures? For polystyrene (aromatic-rich) and poly(methyl methacrylate) (solely aliphatic) latex particles impinging at around 5 km s−1 onto metal targets, we find that sufficient residue is retained at the impact site to permit identification of a carbon-rich projectile, but not of the particular molecules involved, nor is it currently possible to discriminate between aromatic-rich and solely aliphatic particles. This suggests that an alternative analytical method to simple impacts on metal targets is required to enable successful collection of organic samples in a fly-by Enceladus mission, or, alternatively, a lower encounter speed is required.

scholarly journals Organic Molecules: Is It Possible To Distinguish Aromatics From Aliphatics Collected By Space Missions in High-Speed Impacts

Sci ◽  
2020 ◽  
Vol 2 (1) ◽  
pp. 12
Author(s):  
Mark Burchell ◽  
Kathryn Harriss
Keyword(s):  
High Speed ◽  
Organic Molecules ◽  
Chemical Structures ◽  
Surface Ocean ◽  
Life Itself ◽  
Organic Particles ◽  
Open Question ◽  
The Impact ◽  
The Relationship ◽  
Complex Organic

A prime site of astrobiological interest within the Solar System is the interior ocean of Enceladus. This ocean has already been shown to contain organic molecules, and is thought to have the conditions necessary for more complex organic biomolecules to emerge and potentially even life itself. This sub-surface ocean has been accessed by Cassini, an unmanned spacecraft that interacted with the water plumes ejected naturally from Enceladus. The encounter speed with these plumes and their contents, was 5 km s−1 and above. Encounters at such speeds allow analysis of vapourised material from submicron-sized particles within the plume, but sampling micron-sized particles remains an open question. The latter particles can impact metal targets exposed on the exterior of future spacecraft, producing impact craters lined with impactor residue, which can then be analysed. Although there is considerable literature on how mineral grains behave in such high-speed impacts, and also on the relationship between the crater residue and the original grain composition, far less is known regarding the behaviour of organic particles. Here we consider a deceptively simple yet fundamental scientific question: for impacts at speeds of around 5−6 kms−1 would the impactor residue alone be sufficient to enable us to recognise the signature conferred by organic particles? Furthermore, would it be possible to identify the organic molecules involved, or at least distinguish between aromatic and aliphatic chemical structures? For polystyrene (aromatic-rich) and poly(methyl methacrylate) (solely aliphatic) latex particles impinging at around 5 km s-1 onto metal targets, we find that sufficient residue is retained at the impact site to permit identification of a carbon-rich projectile, but not of the particular molecules involved, nor is it currently possible to discriminate between aromatic-rich and solely aliphatic particles. This suggests that an alternative analytical method to simple impacts on metal targets is required to enable successful collection of organic samples in a fly-by Enceladus mission, or, alternatively, a lower encounter speed is required.

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