Related Experiment Video
Updated: Apr 12, 2026
06:26
Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
7.7K
Structural changes in amorphous solid water films on heating to 120-140 K and 150-160 K seen by positronium
1Department of Physics, University of Bath, Bath BA2 7AY, UK.
Summary
Positronium annihilation spectroscopy revealed structural changes in amorphous solid water films. These changes, observed during heating, indicate a glass transition and potential structural reorganization or relaxation processes.
Area of Science:
- Materials Science
- Physical Chemistry
- Condensed Matter Physics
Background:
- Amorphous solid water (ASW) is a relevant material in astrochemistry and planetary science.
- Understanding ASW structural dynamics is crucial for various physical and chemical processes.
Purpose of the Study:
- To investigate structural changes in amorphous solid water films.
- To determine the thermal transitions and associated activation energies in ASW.
Main Methods:
- Vapour deposition of ASW films on a copper substrate at 75 K.
- Annealing at 120 K to induce pore collapse.
- Positronium annihilation spectroscopy (PAS) for structural analysis.
Main Results:
- Observed structural changes in ASW films within two temperature ranges: 122-139 K and 150-162 K.
- Identified a glass transition around 122-139 K with an activation energy of 0.266(3) eV.
- Detected molecular disorder and relaxation phenomena around 150-162 K with an activation energy of 0.47(2) eV.
Conclusions:
- The study proposes that the 122-139 K transition corresponds to the glass transition of ASW.
- The 150-162 K transition suggests either crystalline lattice reorganization or amorphous structure relaxation via defect migration.
- PAS is effective in probing subtle structural dynamics in amorphous solid water.
More Related Videos
Related Concept Videos
02:39Phase Transitions: Melting and Freezing
15.7K
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
15.7K
01:23States of Water
58.4K
Water exists in any one of the three classical states: solid (ice), liquid (water), and gas (steam or water vapor). The state of water depends on i) the intermolecular forces that draw molecules together and ii) the kinetic energy that leads to movements that pull them apart.
Water freezes when the intermolecular forces are greater than the kinetic energy. Unlike most other substances, water is less dense in its solid state than in its liquid state. This is because each water molecule can form...
Water freezes when the intermolecular forces are greater than the kinetic energy. Unlike most other substances, water is less dense in its solid state than in its liquid state. This is because each water molecule can form...
58.4K
01:27Atomic Spectroscopy: Effects of Temperature
1.2K
Atomization, converting samples into gas-phase atoms and ions, is essential for atomic spectroscopy. The flame temperature required for atomization affects the efficiency of the atomic spectroscopic methods by increasing the atomization efficiency and the relative population of the excited and ground states.
At thermal equilibrium, the relative populations of excited and ground state atoms can be estimated using the Maxwell–Boltzmann distribution. For example, an increase in temperature...
At thermal equilibrium, the relative populations of excited and ground state atoms can be estimated using the Maxwell–Boltzmann distribution. For example, an increase in temperature...
1.2K
02:44Heating and Cooling Curves
29.0K
When a substance—isolated from its environment—is subjected to heat changes, corresponding changes in temperature and phase of the substance is observed; this is graphically represented by heating and cooling curves.
For instance, the addition of heat raises the temperature of a solid; the amount of heat absorbed depends on the heat capacity of the solid (q = mcsolidΔT). According to thermochemistry, the relation between the amount of heat absorbed or released by a substance, q, and its...
For instance, the addition of heat raises the temperature of a solid; the amount of heat absorbed depends on the heat capacity of the solid (q = mcsolidΔT). According to thermochemistry, the relation between the amount of heat absorbed or released by a substance, q, and its...
29.0K
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
1.8K
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
1.8K
02:39Phase Transitions: Vaporization and Condensation
22.2K
The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize (convert into vapor). The process is called vaporization—a surface phenomenon. Vaporization occurs when the thermal motion of the molecules overcome the intermolecular forces, and the molecules (at the surface) escape into the gaseous state. When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules...
22.2K