Second-harmonic generation at the liquid/air interface
Second-harmonic generation at the liquid/air interface
The technique of second-harmonic generation has been used to investigate the interfacial properties of several systems. These include H2O/air, NaCl(aq)/air, H2SO4(aq) / air, phenol(aq)/air and the surfaces of various specially prepared metals. Several different laser systems were used during the course of this work providing a range of frequencies, powers, and repetition rates.
The temperature dependence of the second-harmonic response from the H2O/air interface was investigated from 20 to 70oC. Over his temperature range, the magnitude of the second-harmonic signal was found to decrease by ~20%. In addition, evidence was found for an angular distribution, of the interfacial molecules, the average of which tilts further from the surface normal as the temperature increases. The indication is an augmentation of the orientational distribution of the surface molecules, which can be accounted for as a result of increased thermal agitation. NaCl was used to study the effects of adding an electrolytic substance on the interfacial properties of the H2O/air system. Although an increase in the second-harmonic response was detected with increasing NaCl concentrations, the components of the second-order surface susceptibility showed no significant fluctuation.
Concentration and temperature dependence studies of the second-harmonic response, were performed on the H2SO4(aq)/air interface. The results showed a significant dependence of the second-order surface susceptibility on acid concentration. Three phases of behaviour were discovered at low, equi-molar, and high molarities. Increasing temperature provided evidence for a shifting of the various phases to higher concentrations.
Polarisations dependence studies were performed on the phenol(aq)/air interface for concentrations up to 0.5M. The magnitude of the second-harmonic follows the increase in surface coverage, as measured by neutron reflection experiments [Z.X.Li, R.K.Thomas, A.R.Rennie and J. Penifold, J. Phys. Chem B, 102, 185-192, (1998)]. The average molecular orientation of the interfacial phenol is found to remain constant over the concentration range 0.1 to 0.5 M.
The surface of mesoporous and continuous platinum films was investigated with polarisation dependence scans for the second-harmonic signal. The result was a variation of detected signal from rotation of the sample. There is evidence that the gold substrate influenced the results of the scans of the mesoporous samples. The success of this experiment was hindered by the inability to align consistently with molecular domains.
University of Southampton
Fordyce, Adam James Graham
1999
Fordyce, Adam James Graham
Fordyce, Adam James Graham
(1999)
Second-harmonic generation at the liquid/air interface.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The technique of second-harmonic generation has been used to investigate the interfacial properties of several systems. These include H2O/air, NaCl(aq)/air, H2SO4(aq) / air, phenol(aq)/air and the surfaces of various specially prepared metals. Several different laser systems were used during the course of this work providing a range of frequencies, powers, and repetition rates.
The temperature dependence of the second-harmonic response from the H2O/air interface was investigated from 20 to 70oC. Over his temperature range, the magnitude of the second-harmonic signal was found to decrease by ~20%. In addition, evidence was found for an angular distribution, of the interfacial molecules, the average of which tilts further from the surface normal as the temperature increases. The indication is an augmentation of the orientational distribution of the surface molecules, which can be accounted for as a result of increased thermal agitation. NaCl was used to study the effects of adding an electrolytic substance on the interfacial properties of the H2O/air system. Although an increase in the second-harmonic response was detected with increasing NaCl concentrations, the components of the second-order surface susceptibility showed no significant fluctuation.
Concentration and temperature dependence studies of the second-harmonic response, were performed on the H2SO4(aq)/air interface. The results showed a significant dependence of the second-order surface susceptibility on acid concentration. Three phases of behaviour were discovered at low, equi-molar, and high molarities. Increasing temperature provided evidence for a shifting of the various phases to higher concentrations.
Polarisations dependence studies were performed on the phenol(aq)/air interface for concentrations up to 0.5M. The magnitude of the second-harmonic follows the increase in surface coverage, as measured by neutron reflection experiments [Z.X.Li, R.K.Thomas, A.R.Rennie and J. Penifold, J. Phys. Chem B, 102, 185-192, (1998)]. The average molecular orientation of the interfacial phenol is found to remain constant over the concentration range 0.1 to 0.5 M.
The surface of mesoporous and continuous platinum films was investigated with polarisation dependence scans for the second-harmonic signal. The result was a variation of detected signal from rotation of the sample. There is evidence that the gold substrate influenced the results of the scans of the mesoporous samples. The success of this experiment was hindered by the inability to align consistently with molecular domains.
This record has no associated files available for download.
More information
Published date: 1999
Identifiers
Local EPrints ID: 463835
URI: http://eprints.soton.ac.uk/id/eprint/463835
PURE UUID: aea8a4a5-548d-42fd-9bb0-c943bc15034d
Catalogue record
Date deposited: 04 Jul 2022 20:57
Last modified: 04 Jul 2022 20:57
Export record
Contributors
Author:
Adam James Graham Fordyce
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics