Dr Joshua Machacek
Areas of expertise
- Atomic And Molecular Physics 020201
- Atomic, Molecular, Nuclear, Particle And Plasma Physics Not Elsewhere Classified 020299
- Classical And Physical Optics 020501
- Quantum Physics Not Elsewhere Classified 020699
- Space And Solar Physics 020109
Available student projects
Fragmentation of molecules by positronium
Positronium is a bound state between an electron and a positron. It is hydrogen-like with a binding energy half that of hydrogen. Positronium has been found to scatter like an electron for the same velocity. Electrons can fragment molecules by temporary attaching leading to fragmentation. This project will explore the fragmentation of molecules in positronium scattering with molecules.
Benchmark positron scattering experiments
Using the atomic and molecular physics positron beam at the ANU, the student will undertake measurements of positron scattering from simple targets, providing high accuracy data to test recent theoretical calculations.
Positrons and Dust Grains
Positron emitters are embedded in clouds of dust grains produced by supernova. This project will explore the transport of positrons in dust grains using Monte-Carlo techniques to improve our understanding of positron transport in an astrophysically relevant setting.
Publications
- Vogl, T, Sripathy, K, Sharma, A et al. 2019, 'Radiation tolerance of two-dimensional material-based devices for space applications', Nature Communications, vol. 10, no. 1202, pp. 1-10.
- Cocks, D, Chaudhary, H & Machacek, J 2019, 'Benchmark for the Determination of the Positronium Formation Fraction in Interstellar Media', The Astrophysical Journal, vol. 878, no. 123, pp. 1-8.
- Babij, T, Machacek, J, Murtagh, D et al 2018, 'Near-Threshold Ionization of Argon by Positron Impact', Physical Review Letters, vol. 120, no. 11, pp. 1-4.
- Stevens, D, Babij, T, Machacek, J et al. 2018, 'Positron scattering from pyridine', Journal of Chemical Physics, vol. 148, no. 14, p. 7.
- Machacek, J & McEachran, R 2018, 'Partial wave analysis for folded differential cross sections', Journal of Physics B: Atomic, Molecular and Optical Physics, vol. 51, no. 6, pp. 1-8.
- Panther, F, Seitenzahl, I, Crocker, R et al 2018, 'Effect of positron-alkali metal atom interactions in the diffuse interstellar medium', Physical Review D, vol. 98, no. 2, pp. 1-7.
- Machacek, J, Babij, T, Murtagh, D et al 2017, 'A new technique for measuring positron impact direct ionisation', European Physical Journal D: Atomic, Molecular, Optical and Plasma Physics, vol. 71, no. 328, pp. 5pp.
- Boadle, R, Babij, T, Machacek, J et al 2016, 'Low-energy elastic and inelastic scattering of positrons from argon', Physical Review A - Atomic, Molecular, and Optical Physics, vol. 93, no. 2, pp. 022712 (6pp).
- Machacek, J, Blanco, F, Garcia, G et al 2016, 'Regularities in positronium formation for atoms and molecules', Journal of Physics B: Atomic, Molecular and Optical Physics, vol. 49, no. 6, p. 064003.
- Blanco, F, Roldan, A, Krupa, K et al 2016, 'Scattering data for modelling positron tracks in gaseous and liquid water', Journal of Physics B: Atomic, Molecular and Optical Physics, vol. 49, no. 14, pp. 145001 (10pp).
- Machacek, J, Mahapatra, D, Schultz, D et al. 2015, 'SOLAR-WIND ION-DRIVEN X-RAY EMISSION FROM COMETARY AND PLANETARY ATMOSPHERES: MEASUREMENTS AND THEORETICAL PREDICTIONS OF CHARGE-EXCHANGE CROSS-SECTIONS AND EMISSION SPECTRA FOR O6+ + H2O, CO, CO2, CH4, N-2, NO, N2O, AND Ar', The Astrophysical Journal, vol. 809, no. 1, pp. 1-8.
- Machacek, J, Mahapatra, D, Schultz, D et al 2015, 'Measurements and Theoretical Predictions of Charge Exchange Cross Sections and Emission Spectra for O6+ with H2O, CO, CO2, CH4, N2, NO, N2O and Ar', International Conference on Photonic, Electronic and Atomic Collisions, ICPEAC 2015, ed. .Garcia G.Rabadan I., IOP Publishing, United Kingdom, pp. -.
- Machacek, J, Tattersall, W, Boadle, R et al 2015, 'Positron scattering from Biomolecules', Journal of Physics: Conference Series (Print), vol. 635, pp. -.
- Machacek, J, Mahapatra, D, Schultz, D et al 2014, 'Measurement and calculation of absolute single- and double-charge-exchange cross sections for O6+ ions at 1.17 and 2.33 keV/u impacting He and H-2', Physical Review A: Atomic, Molecular and Optical Physics, vol. 90, no. 5, p. 052708.
- Mahapatra, D, Chutjian, A, Machacek, J et al. 2014, 'SIZE DISTRIBUTION OF POSSIBLE DUST CARRIERS FOR THE EXTENDED RED EMISSION', The Astrophysical Journal, vol. 790, no. 2, pp. 1-5.
- Tattersall, W, Chiari, L, Machacek, J et al 2014, 'Positron interactions with water-total elastic, total inelastic, and elastic differential cross section measurements', Journal of Chemical Physics, vol. 140, no. 4, pp. 1-9.
- Anderson, E, Boadle, R, Machacek, J et al 2014, 'Low energy positron interactions with uracil-Total scattering, positronium formation, and differential elastic scattering cross sections', The Journal of Chemical Physics, vol. 141, no. 3, pp. 34306-34306.
- Sullivan, J, Chiari, L, Anderson, E et al 2014, 'Low-energy positron and electron scattering from tetrahydrofuran and 3-hydroxy-tetrahydrofuran', 28th International Conference on Photonic, Electronic and Atomic Collisions, ICPEAC 2013, Institute of Physics Publishing, Lanzhou China, p. 1.
- Machacek, J, Buckman, S & Sullivan, J 2014, 'Threshold effects in positron scattering from isoelectronic series of atoms and molecules', Physical Review A: Atomic, Molecular and Optical Physics, vol. 90, no. 4.
- Chiari, L, Anderson, E, Tattersall, W et al 2013, 'Total, elastic, and inelastic cross sections for positron and electron collisions with tetrahydrofuran', Journal of Chemical Physics, vol. 138, no. 7, pp. 1-15.
- Mortensen, T, Deller, A, Isaac, C et al 2013, 'Manipulation of the magnetron orbit of a positron cloud in a Penning trap', Physics of Plasmas, vol. 20, no. 1, pp. 1-5.
- Chiari, L, Palihawadana, P, Machacek, J et al 2013, 'Experimental and theoretical cross sections for positron collisions with 3-hydroxy-tetrahydrofuran', Journal of Chemical Physics, vol. 138, no. 7, pp. 1-11.
- Machacek, J, Anderson, E, Makochekanwa, C et al 2013, 'Positron scattering from molecular hydrogen', Physical Review A: Atomic, Molecular and Optical Physics, vol. 88, no. 4, pp. 1-8.
- Palihawadana, P, Boadle, R, Chiari, L et al 2013, 'Positron scattering from pyrimidine', Physical Review A: Atomic, Molecular and Optical Physics, vol. 88, no. 1, p. 7.
- Caradonna, P, Makochekanwa, C, Jones, A et al 2012, 'A search for Wigner cusps and resonances in positron scattering by atoms and molecules', International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2011), Conference Organising Committee, Belfast, p. 1.
- Palihawadana, P, Machacek, J, Makochekanwa, C et al 2012, 'Electron and positron scattering from pyrimidine', International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2011), Conference Organising Committee, Belfast.
- Machacek, J, Palihawadana, P, Makochekanwa, C et al 2012, 'Trends in positron scattering from biomolecules', International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2011), Conference Organising Committee, Belfast.
- Makochekanwa, C, Machacek, J, Jones, A et al 2012, 'Low energy positron scattering from krypton and xenon', International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2011), Conference Organising Committee, Belfast, p. 1.
- Machacek, J, Boadle, R, Buckman, S et al 2012, 'Search for positron quasibound states in the doubly excited region of the helium atom', Physical Review A: Atomic, Molecular and Optical Physics, vol. 86, no. 6, p. 3.
- Machacek, J, Furst, J, Gay, T et al 2012, 'Orientation of doubly excited states in N-2', Physical Review A: Atomic, Molecular and Optical Physics, vol. 86, no. 4, pp. 041401(R) (5pp).
- Sullivan, J, Machacek, J, Buckman, S et al 2012, 'Comment on "Semiempirical potentials for positron scattering by atoms"', Physical Review A: Atomic, Molecular and Optical Physics, vol. 85, p. 3.
- Litaker, E, Machacek, J & Gay, T 2011, 'Detecting an extended light source through a lens', European Journal of Physics, vol. 32, no. 4, pp. 1107-1116.
- Sullivan, J, Makochekanwa, C, Jones, A et al 2011, 'Forward angle scattering effects in the measurement of total cross sections for positron scattering', Journal of Physics B: Atomic, Molecular and Optical Physics, vol. 44, no. 3, p. 5.
- Sullivan, J, Caradonna, P, Jones, A et al 2011, 'Low energy positron interactions with rare gas atoms: threshold features and benchmark cross sections', International Workshop on Slow Positron Beam Techniques 2010 - SLOPOS12, ed. Stephen Buckman, James Sullivan and Ronald White, Institute of Physics Publishing, United Kingom.
- Jones, A, Makochekanwa, C, Caradonna, P et al 2011, 'Positron scattering from neon and argon', Physical Review A: Atomic, Molecular and Optical Physics, vol. 83, no. 3.
- Machacek, J, Andrianarijaona, V, Furst, J et al. 2011, 'Production of excited atomic hydrogen and deuterium from H-2, HD and D-2 photodissociation', Journal of Physics B: Atomic, Molecular and Optical Physics, vol. 44, no. 4, p. 7.
- Makochekanwa, C, Machacek, J, Jones, A et al 2011, 'Low-energy positron interactions with krypton', Physical Review A: Atomic, Molecular and Optical Physics, vol. 83, no. 3, p. 12.
- Machacek, J, Makochekanwa, C, Jones, A et al 2011, 'Low-energy positron interactions with xenon', New Journal of Physics, vol. 13, no. 125004, p. 19.
- Jones, A, Caradonna, P, Makochekanwa, C et al 2010, 'Observation of Threshold Effects in Positron Scattering from the Noble Gases', Physical Review Letters, vol. 105, no. 7, p. 4.
Projects and Grants
Grants information is drawn from ARIES. To add or update Projects or Grants information please contact your College Research Office.
- Can positronium fragment complex molecules? (Primary Investigator)
