Charles Figura - Academia.edu (original) (raw)
Papers by Charles Figura
The Astrophysical Journal
We present initial results from the K-band focal plane array Examinations of Young STellar Object... more We present initial results from the K-band focal plane array Examinations of Young STellar Object Natal Environments (KEYSTONE) survey, a large project on the 100m Green Bank Telescope mapping ammonia emission across eleven giant molecular clouds at distances of 0.9 − 3.0 kpc (Cygnus X North,
ABSTRACT Massive stars inject enormous amounts of energy into their environments in the form of U... more ABSTRACT Massive stars inject enormous amounts of energy into their environments in the form of UV radiation and molecular outflows, creating HII regions and enriching local chemistry. These effects provide feedback mechanisms that aid in regulating star formation in the region, and may trigger the formation of subsequent generations of stars. Understanding the mechanics of massive star formation presents an important key to understanding this process and its role in shaping the dynamics of galactic structure. The Red MSX Source (RMS) survey is a multi-wavelength investigation of ~1200 massive young stellar objects (MYSO) and ultra-compact HII (UCHII) regions identified from a sample of colour-selected sources from the Midcourse Space Experiment (MSX) point source catalog and Two Micron All Sky Survey. We present a study of over 900 MYSO and UCHII regions investigated by the RMS survey. We review the methods used to determine distances, and investigate the radial galactocentric distribution of these sources in context with the observed structure of the galaxy. The distribution of MYSO and UCHII regions is found to be spatially correlated with the spiral arms and galactic bar. We examine the radial distribution of MYSOs and UCHII regions and find variations in the star formation rate between the inner and outer Galaxy and discuss the implications for star formation throughout the galactic disc.
Nonlinear Optical Properties of Organic Materials X, 1997
We demonstrate, for the first time, that a new ionically self-assembled monolayer (ISAM) techniqu... more We demonstrate, for the first time, that a new ionically self-assembled monolayer (ISAM) technique for thin film deposition can be employed to fabricate materials possessing the noncentrosymmetry that is requisite for a second order, nonlinear optical response. Using two different commercially-available polyelectrolytes, we have produced ISAM nonlinear optical thin films with values comparable to that of quartz. As a result of the ionic attraction between successive layers, the ISAM films self-assemble into a noncentrosymmetric structure that has exhibited no measureable decay of at room temperature over a period of more than four months. The x2 of ISAM films has been examined by second harmonic generation using a fundamental wavelength of 1200 nm. The second harmonic intensity of the films exhibits the expected quadratic dependences on fundamental intensity and film thickness while the polarization dependence is consistent with orientation of the chromophore dipole moment perpendicular to the substrate.
Summary form only given. Here we report measurements of two fullerene-based materials, derivative... more Summary form only given. Here we report measurements of two fullerene-based materials, derivatives of C/sub 60/ and higher fullerenes, in the wavelength region 680 to 880 nm and show that the weak ground-state absorptions they possess extend the efficient reverse saturable absorption (RSA) of the fullerenes to longer wavelengths than is found for C/sub 60/ alone. The optical-limiting measurements from 680 to 880 nm are performed with a pulsed dye laser pumped by the frequency-doubled output of an 8 ns pulsewidth, Q-switched Nd:YAG laser.
Organic Thin …, 1999
... also present results regarding novel ISAM structures including nonpolymeric chromphores as we... more ... also present results regarding novel ISAM structures including nonpolymeric chromphores as well as biorecognition (as opposed to ionic) interactions. These approcahes increase the net orientational chromophore alignment. 1. G. Decher, JD Hong, and J. Schmitt, Thin Solid ...
We report two separate studies of the nonlinear optical properties of unique fullerene materials.... more We report two separate studies of the nonlinear optical properties of unique fullerene materials. Degenerate four- wave mixing measurements of the endohedral metallofullerene Er2 at C82 at 1064 nm show that the third order susceptibility is increased by more than two orders of magnitude relative to the empty cage fullerenes as a result of the metal-to-cage charge transfer. Optical limiting studies of C60 derivatives and higher fullerenes in the 680 to 880 nm spectral region demonstrate that these materials are strong reverse saturable absorbers at wavelengths where C60 itself is transparent. The tremendous variety of available fullerene-derived structures provides important opportunities for optimization of nonlinear optical responses.
The wavelength-dependence of optical limiting in the reverse saturable absorber C60 has been stud... more The wavelength-dependence of optical limiting in the reverse saturable absorber C60 has been studied in detail over a large spectral range and compared to that of two phthalocyanines. The reverse saturable absorption of C60 is found to increase at wavelengths longer than the standardly measured 532 nm. The optical limiting data have been analyzed in terms of the dynamical population
We propose to image a sample of massive young stellar objects towards which both strong ammonia (... more We propose to image a sample of massive young stellar objects towards which both strong ammonia (1,1) and (2,2) emission has previously been detected. The aim of these observations is to probe the physical conditions of the cores in which massive stars formation is taking place. Ammonia is a dense gas tracer and an excellent probe of the properties of
Proc. …, 2000
Thermal Stability and Immersion Solution Dependence of Second Order Nonlinear Optical Ionically S... more Thermal Stability and Immersion Solution Dependence of Second Order Nonlinear Optical Ionically Self-Assembled Films C. Figura3*, PJ Neymana, D ... ISAM NLO films exhibit excellent long-term temporal stability of % \ having shown no decay over a period of nearly three years. ...
MRS Proceedings, 1999
... "(2) =2 ( Al (1) X Arf 30 Page 3. 800 700 600 500 Cl400 a X 300 200 b 100 -'fA 0 0 ... more ... "(2) =2 ( Al (1) X Arf 30 Page 3. 800 700 600 500 Cl400 a X 300 200 b 100 -'fA 0 0 200 400 600 Reference Intensity Figure 2. Comparison of second-harmonic intensities observed for a 30-bilayer Poly S-1 19 EF-ESAM film (a) and a 68-bilayer Poly S-1 19 ESAM film (b). ...
Proceedings of SPIE - The International Society for Optical Engineering
We report two separate studies of the nonlinear optical properties of unique fullerene materials.... more We report two separate studies of the nonlinear optical properties of unique fullerene materials. Degenerate four- wave mixing measurements of the endohedral metallofullerene Er2 at C82 at 1064 nm show that the third order susceptibility is increased by more than two orders of magnitude relative to the empty cage fullerenes as a result of the metal-to-cage charge transfer. Optical limiting studies of C60 derivatives and higher fullerenes in the 680 to 880 nm spectral region demonstrate that these materials are strong reverse saturable absorbers at wavelengths where C60 itself is transparent. The tremendous variety of available fullerene-derived structures provides important opportunities for optimization of nonlinear optical responses.
Summary form only given. Here we report measurements of two fullerene-based materials, derivative... more Summary form only given. Here we report measurements of two fullerene-based materials, derivatives of C/sub 60/ and higher fullerenes, in the wavelength region 680 to 880 nm and show that the weak ground-state absorptions they possess extend the efficient reverse saturable absorption (RSA) of the fullerenes to longer wavelengths than is found for C/sub 60/ alone. The optical-limiting measurements from 680 to 880 nm are performed with a pulsed dye laser pumped by the frequency-doubled output of an 8 ns pulsewidth, Q-switched Nd:YAG laser.
The Astrophysical Journal
We present initial results from the K-band focal plane array Examinations of Young STellar Object... more We present initial results from the K-band focal plane array Examinations of Young STellar Object Natal Environments (KEYSTONE) survey, a large project on the 100m Green Bank Telescope mapping ammonia emission across eleven giant molecular clouds at distances of 0.9 − 3.0 kpc (Cygnus X North,
ABSTRACT Massive stars inject enormous amounts of energy into their environments in the form of U... more ABSTRACT Massive stars inject enormous amounts of energy into their environments in the form of UV radiation and molecular outflows, creating HII regions and enriching local chemistry. These effects provide feedback mechanisms that aid in regulating star formation in the region, and may trigger the formation of subsequent generations of stars. Understanding the mechanics of massive star formation presents an important key to understanding this process and its role in shaping the dynamics of galactic structure. The Red MSX Source (RMS) survey is a multi-wavelength investigation of ~1200 massive young stellar objects (MYSO) and ultra-compact HII (UCHII) regions identified from a sample of colour-selected sources from the Midcourse Space Experiment (MSX) point source catalog and Two Micron All Sky Survey. We present a study of over 900 MYSO and UCHII regions investigated by the RMS survey. We review the methods used to determine distances, and investigate the radial galactocentric distribution of these sources in context with the observed structure of the galaxy. The distribution of MYSO and UCHII regions is found to be spatially correlated with the spiral arms and galactic bar. We examine the radial distribution of MYSOs and UCHII regions and find variations in the star formation rate between the inner and outer Galaxy and discuss the implications for star formation throughout the galactic disc.
Nonlinear Optical Properties of Organic Materials X, 1997
We demonstrate, for the first time, that a new ionically self-assembled monolayer (ISAM) techniqu... more We demonstrate, for the first time, that a new ionically self-assembled monolayer (ISAM) technique for thin film deposition can be employed to fabricate materials possessing the noncentrosymmetry that is requisite for a second order, nonlinear optical response. Using two different commercially-available polyelectrolytes, we have produced ISAM nonlinear optical thin films with values comparable to that of quartz. As a result of the ionic attraction between successive layers, the ISAM films self-assemble into a noncentrosymmetric structure that has exhibited no measureable decay of at room temperature over a period of more than four months. The x2 of ISAM films has been examined by second harmonic generation using a fundamental wavelength of 1200 nm. The second harmonic intensity of the films exhibits the expected quadratic dependences on fundamental intensity and film thickness while the polarization dependence is consistent with orientation of the chromophore dipole moment perpendicular to the substrate.
Summary form only given. Here we report measurements of two fullerene-based materials, derivative... more Summary form only given. Here we report measurements of two fullerene-based materials, derivatives of C/sub 60/ and higher fullerenes, in the wavelength region 680 to 880 nm and show that the weak ground-state absorptions they possess extend the efficient reverse saturable absorption (RSA) of the fullerenes to longer wavelengths than is found for C/sub 60/ alone. The optical-limiting measurements from 680 to 880 nm are performed with a pulsed dye laser pumped by the frequency-doubled output of an 8 ns pulsewidth, Q-switched Nd:YAG laser.
Organic Thin …, 1999
... also present results regarding novel ISAM structures including nonpolymeric chromphores as we... more ... also present results regarding novel ISAM structures including nonpolymeric chromphores as well as biorecognition (as opposed to ionic) interactions. These approcahes increase the net orientational chromophore alignment. 1. G. Decher, JD Hong, and J. Schmitt, Thin Solid ...
We report two separate studies of the nonlinear optical properties of unique fullerene materials.... more We report two separate studies of the nonlinear optical properties of unique fullerene materials. Degenerate four- wave mixing measurements of the endohedral metallofullerene Er2 at C82 at 1064 nm show that the third order susceptibility is increased by more than two orders of magnitude relative to the empty cage fullerenes as a result of the metal-to-cage charge transfer. Optical limiting studies of C60 derivatives and higher fullerenes in the 680 to 880 nm spectral region demonstrate that these materials are strong reverse saturable absorbers at wavelengths where C60 itself is transparent. The tremendous variety of available fullerene-derived structures provides important opportunities for optimization of nonlinear optical responses.
The wavelength-dependence of optical limiting in the reverse saturable absorber C60 has been stud... more The wavelength-dependence of optical limiting in the reverse saturable absorber C60 has been studied in detail over a large spectral range and compared to that of two phthalocyanines. The reverse saturable absorption of C60 is found to increase at wavelengths longer than the standardly measured 532 nm. The optical limiting data have been analyzed in terms of the dynamical population
We propose to image a sample of massive young stellar objects towards which both strong ammonia (... more We propose to image a sample of massive young stellar objects towards which both strong ammonia (1,1) and (2,2) emission has previously been detected. The aim of these observations is to probe the physical conditions of the cores in which massive stars formation is taking place. Ammonia is a dense gas tracer and an excellent probe of the properties of
Proc. …, 2000
Thermal Stability and Immersion Solution Dependence of Second Order Nonlinear Optical Ionically S... more Thermal Stability and Immersion Solution Dependence of Second Order Nonlinear Optical Ionically Self-Assembled Films C. Figura3*, PJ Neymana, D ... ISAM NLO films exhibit excellent long-term temporal stability of % \ having shown no decay over a period of nearly three years. ...
MRS Proceedings, 1999
... "(2) =2 ( Al (1) X Arf 30 Page 3. 800 700 600 500 Cl400 a X 300 200 b 100 -'fA 0 0 ... more ... "(2) =2 ( Al (1) X Arf 30 Page 3. 800 700 600 500 Cl400 a X 300 200 b 100 -'fA 0 0 200 400 600 Reference Intensity Figure 2. Comparison of second-harmonic intensities observed for a 30-bilayer Poly S-1 19 EF-ESAM film (a) and a 68-bilayer Poly S-1 19 ESAM film (b). ...
Proceedings of SPIE - The International Society for Optical Engineering
We report two separate studies of the nonlinear optical properties of unique fullerene materials.... more We report two separate studies of the nonlinear optical properties of unique fullerene materials. Degenerate four- wave mixing measurements of the endohedral metallofullerene Er2 at C82 at 1064 nm show that the third order susceptibility is increased by more than two orders of magnitude relative to the empty cage fullerenes as a result of the metal-to-cage charge transfer. Optical limiting studies of C60 derivatives and higher fullerenes in the 680 to 880 nm spectral region demonstrate that these materials are strong reverse saturable absorbers at wavelengths where C60 itself is transparent. The tremendous variety of available fullerene-derived structures provides important opportunities for optimization of nonlinear optical responses.
Summary form only given. Here we report measurements of two fullerene-based materials, derivative... more Summary form only given. Here we report measurements of two fullerene-based materials, derivatives of C/sub 60/ and higher fullerenes, in the wavelength region 680 to 880 nm and show that the weak ground-state absorptions they possess extend the efficient reverse saturable absorption (RSA) of the fullerenes to longer wavelengths than is found for C/sub 60/ alone. The optical-limiting measurements from 680 to 880 nm are performed with a pulsed dye laser pumped by the frequency-doubled output of an 8 ns pulsewidth, Q-switched Nd:YAG laser.