Femtosecond-to-nanosecond nonlinear spectroscopy of polymethine molecules
Richard S. Lepkowicz, Claudiu M. Cirloganu, Jie Fu, Olga V. Przhonska, David J. Hagan, Eric W. Van Stryland, Mikhail V. Bondar, Yuriy L. Slominsky, and Alexei D. Kachkovski
Richard S. Lepkowicz,1,1
Claudiu M. Cirloganu,1
Jie Fu,1
Olga V. Przhonska,2
David J. Hagan,3
Eric W. Van Stryland,3
Mikhail V. Bondar,4
Yuriy L. Slominsky,5
and Alexei D. Kachkovski5
1Center for Research and Education in Optics and Lasers and Florida Photonics Center of Excellence, College of Optics and Photonics, University of Central Florida, Florida 32816-2700 USA
2Center for Research and Education in Optics and Lasers and Florida Photonics Center of Excellence, College of Optics and Photonics, University of Central Florida, Florida 32816-2700, and Institute of Physics, National Academy of Sciences, Prospect Nauki 46, Kiev, 03028, Ukraine
3Center for Research and Education in Optics and Lasers and Florida Photonics Center of Excellence, College of Optics and Photonics, University of Central Florida, Florida 32816-2700, and Department of Physics, University of Central Florida, Orlando, Florida 32816-2700 USA
4Institute of Physics, National Academy of Sciences, Prospect Nauki 46, Kiev, 03028, Ukraine
5Institute of Organic Chemistry, National Academy of Sciences, Murmanskaya 5, Kiev, 03094, Ukraine
Current address, Optical Sciences Division, U.S. Naval Research Laboratory, Washington D.C., 20375-5338.
Richard S. Lepkowicz, Claudiu M. Cirloganu, Jie Fu, Olga V. Przhonska, David J. Hagan, Eric W. Van Stryland, Mikhail V. Bondar, Yuriy L. Slominsky, and Alexei D. Kachkovski, "Femtosecond-to-nanosecond nonlinear spectroscopy of polymethine molecules," J. Opt. Soc. Am. B 22, 2664-2685 (2005)
The linear and nonlinear optical properties of a series of polymethine molecules are investigated to study the effects of molecular structure and the host environment on overall nonlinear absorption performance. The linear characterization includes measuring the solvatochromic shifts between absorption and fluorescence peaks and studying the excited-state orientational diffusion kinetics. The nonlinear characterization involves measuring the excited-state absorption spectra with a femtosecond white-light-continuum pump–probe technique and performing Z scans and nonlinear transmission measurements from the picosecond to the nanosecond time regimes. The results of these experiments allow us to develop an energy-level structure for the polymethines, which accurately predicts nonlinear absorption properties from the picosecond to the nanosecond time regimes. From this model we are able to identify the key molecular parameters for improved nonlinear absorption.
Olga V. Przhonska, Jin Hong Lim, David J. Hagan, Eric W. Van Stryland, Mikhail V. Bondar, and Yurij L. Slominsky J. Opt. Soc. Am. B 15(2) 802-809 (1998)
Jie Fu, Lazaro A. Padilha, David J. Hagan, Eric W. Van Stryland, Olga V. Przhonska, Mikhail V. Bondar, Yuriy L. Slominsky, and Alexei D. Kachkovski J. Opt. Soc. Am. B 24(1) 67-76 (2007)
Jie Fu, Lazaro A. Padilha, David J. Hagan, Eric W. Van Stryland, Olga V. Przhonska, Mikhail V. Bondar, Yuriy L. Slominsky, and Alexei D. Kachkovski J. Opt. Soc. Am. B 24(1) 56-66 (2007)
Richard L. Sutherland, Mark C. Brant, Jim Heinrichs, Joy E. Rogers, Jonathan E. Slagle, Daniel G. McLean, and Paul A. Fleitz J. Opt. Soc. Am. B 22(9) 1939-1948 (2005)
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Molecular volumes were calculated as the minimal Van der Waals volumes by using the standard radii of the separate atoms or atomic groups (for example, residues), valence angles, and bond lengths.
Axial dimensions are the distances along the , and z coordinates between the most removed atoms. Calculations of the optimized molecular geometry have been performed in the AM1 approximation with the gradient . It was found that the π-electron system of all molecules is practically planar in the plane, the bond lengths in the chain are almost equalized and equal , and the calculated valence angles are . The methyl groups both in the indolenine residues and in the chain bridges (PD 824 and PD 1659) are out of the chromophore plane. The phenyl substituents near the nitrogen atoms (PD 3428) and in the mesoposition of the chain (PD 1952 and PD 2410) are placed perpendicularly to the plane of the main π-electron system. In contrast to rigidly fixed phenyl groups, the propylene substituents near the nitrogen atoms (PD 2350) are highly flexible for practically barrierless rotation around any carbon―carbon or nitrogen―carbon bonds.
The ground, , and excited, , permanent dipole moments as well as transition moment, , were calculated in the AM1 approximation. The excited-state function was built as the separation of the 25-lowest single excited configurations. The calculated magnitudes are given for the all-trans geometry. It is necessary to note that is large and polarized along the polymethine chain, whereas and are relatively small and directed perpendicular to the chain. For PD 1659 the data are given for the form with the symmetrical charge distribution only.[9]
, first excited-state lifetime; , orientational diffusion time; , higher-excited-state lifetime; , ground-state recovery time; , decay time from the cis to the trans-states. Uncertainties: to to . Uncertainties in and depend on the relative lifetimes between the two of them and their connection by Eq. (3).
DNF, did not fit.
NA, not applicable because parameters were not required.
Peak GS Cross Section—ground-state (GS) cross section at peak spectral position. GS at ESA Peak Cross Section—ground-state cross section at peak spectral position of ESA spectrum. α Peak Pico—ratio of excited-state to ground-state cross sections. α Peak Nano—ratio of excited-state to ground-state cross sections. GS at 532 nm Cross Section—ground-state cross section at 532 nm. α 532 nm—ratio of excited-state to ground-state cross sections at 532 nm. β—ratio of higher-excited-state cross section to ground-state cross section at 532 nm. Uncertainties: peak GS cross section, ; GS at ESA peak cross section, .
NM, not measured.
Table 5
Molecular Parameters Determined from Experiments and Fits
Molecular volumes were calculated as the minimal Van der Waals volumes by using the standard radii of the separate atoms or atomic groups (for example, residues), valence angles, and bond lengths.
Axial dimensions are the distances along the , and z coordinates between the most removed atoms. Calculations of the optimized molecular geometry have been performed in the AM1 approximation with the gradient . It was found that the π-electron system of all molecules is practically planar in the plane, the bond lengths in the chain are almost equalized and equal , and the calculated valence angles are . The methyl groups both in the indolenine residues and in the chain bridges (PD 824 and PD 1659) are out of the chromophore plane. The phenyl substituents near the nitrogen atoms (PD 3428) and in the mesoposition of the chain (PD 1952 and PD 2410) are placed perpendicularly to the plane of the main π-electron system. In contrast to rigidly fixed phenyl groups, the propylene substituents near the nitrogen atoms (PD 2350) are highly flexible for practically barrierless rotation around any carbon―carbon or nitrogen―carbon bonds.
The ground, , and excited, , permanent dipole moments as well as transition moment, , were calculated in the AM1 approximation. The excited-state function was built as the separation of the 25-lowest single excited configurations. The calculated magnitudes are given for the all-trans geometry. It is necessary to note that is large and polarized along the polymethine chain, whereas and are relatively small and directed perpendicular to the chain. For PD 1659 the data are given for the form with the symmetrical charge distribution only.[9]
, first excited-state lifetime; , orientational diffusion time; , higher-excited-state lifetime; , ground-state recovery time; , decay time from the cis to the trans-states. Uncertainties: to to . Uncertainties in and depend on the relative lifetimes between the two of them and their connection by Eq. (3).
DNF, did not fit.
NA, not applicable because parameters were not required.
Peak GS Cross Section—ground-state (GS) cross section at peak spectral position. GS at ESA Peak Cross Section—ground-state cross section at peak spectral position of ESA spectrum. α Peak Pico—ratio of excited-state to ground-state cross sections. α Peak Nano—ratio of excited-state to ground-state cross sections. GS at 532 nm Cross Section—ground-state cross section at 532 nm. α 532 nm—ratio of excited-state to ground-state cross sections at 532 nm. β—ratio of higher-excited-state cross section to ground-state cross section at 532 nm. Uncertainties: peak GS cross section, ; GS at ESA peak cross section, .
NM, not measured.
Table 5
Molecular Parameters Determined from Experiments and Fits