**Surface-Enhanced Spectroscopies**

In conjunction with the Laboratory for Nanophotonics, this group is involved in theoretical understanding of the enhancement of Raman scattering for molecules near or on noble metal nanoparticles. The earliest of these studies was probably the first multi-vibrational-mode spectral simulation of Surface-Enhanced Raman Scattering (SERS), focusing on the contributions of totally-symmetric modes of *p*-aminothiophenol (*p*-mercaptoaniline) adsorbed on metal nanoshells to both Raman scattering and fluorescence. Current interests lie in extending the latter density-matrix treatment to include modes of other symmetry that have been of strong interest in a number of other experiments. This will be in conjunction with experimental efforts in the lab to obtain SERS excitation profiles. The most recent work has focussed on the question of whether Surface-Enhanced Raman Optical Activity (SEROA) can be selective for molecular chirality as is existing Raman Optical Activity. This work has shown that the strong local fields around gold and silver nanoparticles are generally sufficient to interfere with this, but there can exist particular substrate, detection geometry and polarization strategies for which theory predicts both signal enhancement and chiral selectivity.

**Wavelet Technology**

Wavelets offer "universal" bases that potentially allow orthogonality, localization and customizable resolution all at the same time. These aspects make them attractive for future development of highly-automated solutions of the Schrödinger equation in quantum mechanics, the strong local EM fields near metal nanoparticles, and many other applications. Our group has worked on making use of orthogonal compact-support wavelets practical, including systematic control of accuracy, extension to boundary-value and initial-value constraints, and construction of publicly-available C++ code. Most recently, we have constructed a method particularly useful for multidimensional problems in which operator matrices are avoided, strongly increasing the efficiency of wavelet calculations. At the current time we are working on generalizing high-order convolution-filter based methods that transcend the conventional function-representation capabilities (approximation order) of such wavelet bases, at the same time beating the wavelet Gibbs phenomenon that occurs at discontinuities. These are important considerations for applications in QM theory with hard potential walls or in EM theory for interfaces between different dielectric media

R. Acevedo, R. Lombardini and B. R. Johnson, "Matrix-Free Application of Hamiltonian Operators in Coifman Wavelet Bases," J. Chem. Phys. **132**, 244112 (2010)

R. Lombardini, R. Acevedo, N. J. Halas and B. R. Johnson, "Plasmonic Enhancement of Raman Optical Activity in Molecules Near Metal Nanoshells: Theoretical Comparison of Circular Polarization Methods," J. Phys. Chem. C (Martin Moskovits Festschrift) **114**, 7390-7400 (2010)

D. W. Massey, R. Acevedo and B. R. Johnson Additions to the class of symmetric-antisymmetric multiwavelets: Derivation and use as quantum basis functions. *J. Chem. Phys.*, 124 2006: 014101

S. W. Bishnoi, C. J. Rozell, C. S. Levin, M. K. Gheith, B. R. Johnson, D. H. Johnson and N. J. Halas All-Optical Nanoscale pH Meter. *NanoLetters*, 6 2006: 1687-1692

J. W. Gibson and B. R. Johnson Density matrix calculation of surface enhanced Raman scattering for p-mercaptoaniline on silver nanoshells. *J. Chem. Phys.*, 124 2006: 064701

C. D. Griffin, R. Acevedo, D. W. Massey, J. L. Kinsey and B. R. Johnson Multimode wavelet basis calculations via the molecular self-consistent-field plus configuration-interaction method. *J. Chem. Phys.*, 124 2006: 134105

D. K. Sparks and B. R. Johnson Two-dimensional quantum propagation using wavelets in space and time. *J. Chem. Phys.*, 125 2006: 114104

E. K. Lewis, W. C. Haaland, F. Nguyen, D. A. Heller, M. J. Allen, R. R. MacGregor, C. S. Berger, B. Willingham, L. A. Burns, G. B. I. Scott, C. Kittrell, B. R. Johnson, R. F. Curl and M. L. Metzker Color Blind Fluorescence Detection for Four-Color DNA Sequencing. *Proc. Natl. Acad. Sci.*, 102 2005: 5346-5351

H. Wang, R. Acevedo, H. Molle, J. L. Mackey, J. L. Kinsey and B. R. Johnson Multiscale quantum propagation using compact support wavelets in space and time. *J. Chem. Phys.*, 121 2004: 7647-7657

Thierry A. Wasserman, Patrick H. Vaccaro, Johnson, B. The influence of finite bandwidth excitation sources in degenerate four-wave mixing spectroscopy. *J. Chem. Phys.*, 116 2002: 10099-10121

A. Maloney, Kinsey, J., Johnson, B. Wavelets in curvilinear coordinate quantum calculations: H2+ electronic states. *J. Chem. Phys.*, 117 2002: 3548-3557

- B.A. magna cum laude Chemistry, Mathematics, Physics (1975) University of Minnesota
- Ph.D. Chemistry (1981) University of Wisconsin

- Department of Chemistry
- Rice Quantum Institute

- Theoretical chemistry, dissociative and surface-enhanced resonance Raman spectroscopy, four-wave-mixing spectrsocopy, wavelets in quantum mechanics and electromagnetism and signal processing

Phone: (713) 348-5103

Office: Space Science Building, 228