Hugh Richardson
The Condensed Matter & Surface Sciences Colloquium Series presents Hugh Richardson of Ohio University on “Absolute Temperature Measurements Below the Diffraction Limit.” on Thursday, Sept. 17, at 4:10 p.m. in Walter 245.
Abstract: Advances in the prediction and manipulation of thermal energy have been hampered by a lack of control and sensitivity needed to measure thermal behavior at the meso and nanoscales. Several methods have been recently developed to measure temperature at the nanoscale but measuring the absolute temperature at the nanoscale with high spatial (10-100 nm) and temperature (0.1 K) resolution remains challenging. In this talk I will introduce a new optical probe technique using erbium oxide nanoparticle (~ 100 nm) that measures absolute temperature below the diffraction limit. Scanning and measuring the photoluminescence spectrum of an emitting laser trapped erbium oxide nanoparticle over a gold nanostructure immersed in water generates a temperature image. The optical probe thermometer measures the absolute temperature by collecting erbium emission intensities from the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions. These transitions are thermalized and the absolute temperature is calculated from the relative ratio of the emission intensities between the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions using Boltzmann statistics. When the optical thermal sensor size is reduced below the diffraction limited size, then the resolution of temperature measurement is now no longer limited by the point-spread function of the microscope, but is limited by the size of the nanosensor. We use this new technique to measure the temperature where vapor nucleation occurs in degassed and natural water and find that the laser trapped particle is capable of measuring the temperature through the entire nucleation event, including inside the vapor nucleation embryo, where extreme temperatures (~1300 K) are observed initially after vapor nucleation.
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