Frontiers in Spectroscopy

Chemical Physics 880 and 880A

Winter 2007

Course Description: This course will provide students with an overview of topics on the frontier of spectroscopic research. It will exploit internationally renowned lecturers, as well as outstanding OSU faculty, to cover topics ranging from very fundamental to quite applied. General areas to be covered will include fundamental characteristics of molecular quantum structure, electromagnetics, new experimental techniques, remote sensing, ultra-high sensitivity analytical techniques, astrophysical applications, etc. It is planned that the course will be offered multiple times, with topics and speakers varying with each offering. The lecturers for the upcoming Winter quarter are listed below.

Each topic will be covered by lectures on Wednesday and Friday mornings, 9:00-10:18AM, in MP2015.

Thursdays discussions this year only will begin at 9:00-10:18AM on Thursdays in MP2015.

Prerequisites: a previous spectroscopy course at OSU in Chemistry or Physics or prior permission of the instructor

Required Text: None; suggested articles for reading will be supplied prior to the lecture on a given topic.

List of speakers and dates scheduled:

January 10-12 John Stanton, University of Texas at Austin

Readings: Koppel/Cederbaum, Stanton

• Lecture 1
  Overview of vibronic coupling and its effects in spectroscopy. Franck-Condon approximation for diatomic and polyatomic molecules, breakdown of Franck-Condon picture, diabatic v. adiabatic potential energy surfaces, conical intersections, the model Hamiltonian approach of Koeppel, Domcke and Cederbaum (KDC), simple applications.

• Lecture 2
  (for students): Overview of coupled-cluster theory and the equation-of-motion coupled cluster method and their application to spectroscopy. Introduction to the ACES II program system. Q&A session (unrestricted as to topics within theoretical chemistry)

• Lecture 3
  The nitrate radical. History of the spectroscopy, what is and is not understood, analysis of spectra from KDC model Hamiltonian. The question of what we mean by "molecular structure" and does NO3 have one.

January 17-19 David Nesbitt, JILA/University of Colorado
Readings: Docking kinetics..., Slit Discharge IR Spectroscopy..., Quantum-State-Resolved CO2 Scattering..., Jet cooled spectroscopy of H2DO+...

January 31 - February 2 Paul Corkum, NRC
Readings: CJP_Attosecond-review, nature_Tomography, PRL_plasma-perspective, Advances, Corkum_MaxBorn

• Lecture 1: Attosecond Optical Science
  Overview of vibronic coupling and its effects in spectroscopy. Franck-Condon approximation for diatomic and polyatomic molecules, breakdown of Franck-Condon picture, diabatic v. adiabatic potential energy surfaces, conical intersections, the model Hamiltonian approach of Koeppel, Domcke and Cederbaum (KDC), simple applications.
  A revolution is underway in ultrafast optical technology. During the past five years, the minimum pulse duration of optical pulses has fallen from 5 femtoseconds (5x10^-15 sec) to about 100 attoseconds (~10^-16 sec) briefer than the classical period of a ground-state electron in a hydrogen atom. Furthermore, this new attosecond technology allows us to "see" electrons (in the sense that an optical interferometer "sees" light pulses).
  In this presentation, I will describe attosecond techniques, how attosecond electron interferometry is used to image orbitals and how it measures both the spatial and temporal properties of attosecond optical pulses.

• Lecture 2: Student choice:
  Discussion of femtosecond and attosecond techniques
  or
  Discussion of importance of attosecond technology for collision science

• Lecture 3: High Harmonic Transient Grating Spectroscopy
  Transient grating spectroscopy is the method of choice for measuring femtosecond dynamics in solids, liquids or gases whenever background suppression is important. Transient grating measurements are possible even where only a small fraction of the molecules are excited. If we are to truly make molecular movies, then we must extend transient grating spectroscopy to attoseconds.
  At first glance this dream appears totally impossible -- transient grating spectroscopy is based on 4-wave mixing while, you will remember from Lecture 1, attosecond technology requires so many photons that it is no longer useful to count them. I will show that it is surprisingly easy to extend transient grating spectroscopy to extreme nonlinear optics. You will remember from Lecture 1, the phase of the attosecond pulse records the phase of the re-collision electron as interpreted through the transition moment. Therefore, although the transient grating is for XUV light, it is as if the grating were an electron grating. I will show how transient grating spectroscopy allows very subtle changes in molecular dimensions to be observed.

Readings: J. M. Seitzman, A. Ungut, P. H. Paul and R. K. Hanson, Proc. Comb. Inst. 23, 637-644 (1990).
M. C. Thurber and R. K. Hanson, Experiments in Fluids 30, 93-101 (2001).
T. Lee, J. B. Jeffries and R. K. Hanson, Proc. Combust. Inst. 31, ?? (2006).
R. K. Hanson and J. B. Jeffries, paper AIAA-2006-3441.
H. Li, X. Zhou, J. B. Jeffries and R. K. Hanson, paper AIAA -2006-4395.

• Lecture 1 (Wednesday, Feb 14, 2007) - Gas Sensing Based on Tunable Diode Laser Absorption
  Gas sensing based on absorption spectroscopy with cw tunable diode laser sources has progressed rapidly in recent years from a laboratory tool to applications spanning a range of measured parameters and an even wider range of practical and often hostile environments. Most work has utilized diode lasers emitting visible and near-infrared wavelengths, but recently these lasers have been extended into the mid-infrared. This lecture will introduce the primary concepts of tunable diode laser absorption spectroscopy (TDLAS) and overview a range of applications including temperature and species sensing in a variety of combustion and propulsion flows, mass flux sensing in high-speed flows, and laser sensing for combustion control. The lecture will conclude with examples of current work to extend TDLAS to the mid-IR for sensing of hydrocarbons in gaseous and multi-phase flows.

• Lecture 2 (Friday, Feb 16, 2007) - Planar Laser-Induced Fluorescence (PLIF) Imaging of Gaseous Flows
  Planar laser-induced fluorescence imaging, or PLIF, has become an accepted tool for 2-D imaging of gaseous flows. The method typically makes use of a tunable of fixed-wavelength pulsed laser source, resonant with absorption transitions of the molecular species of interest. This may be a reactive species, such as OH, formed in a chemically reacting system, such as combustion, or it may be a stable species, such as acetone or toluene, present as a flowfield tracer. A fraction of the absorbed light is converted to fluorescence and captured on a 2-D digital camera. The result is essentially an instantaneous image proportional to the laser pulse energy and the concentration of the absorbing species. PLIF thus can provide snapshots of complex flow phenomena which are of interest, either for fundamental inquiry or because they are key to understanding the performance of flow facilities such as combustors and propulsion systems. Of course, quantitative application of PLIF requires good understanding of the fundamental processes associated with absorption and fluorescence, that relate the ultimate signal to the flow property of interest, and this need motivates much of the current research on PLIF. The lecture will include an overview of PLIF fundamentals and present example applications for measuring flowfield properties such as species concentration and temperature.

February 28-March 2 Takamasa Momose, University of British Columbia

Readings: Momose97, Momose04, Momose05

• Lecture 1 (Wednesday, Feb 28, 2007) - High-resolution spectroscopy in quantum crystals
  Molecules embedded in quantum crystals possess completely quantized rotational states, to which high-resolution spectroscopy can be applied. The first lecture will review how to treat quantized rotational motion of molecules in a crystal field, and what we can learn from high-resolution spectroscopy of molecules in quantum crystals. A concept of the extended group theory will be introduced in order to classify rotational sates of molecules in a crystal field.

• Lecture 2 (Friday, March 2, 2007) - Chemical dynamics of molecules at low temperatures
  Molecules embedded in quantum crystals are quite useful for the study of chemical dynamics of molecules at low temperatures. This lecture will review chemical dynamics of molecules in quantum crystals such as quantum tunneling reactions, nuclear spin conversion, and nuclear spin state conservation in chemical reactions, and discuss qualitative differences between high-temperature chemistry and low temperature chemistry.

Grading: Satisfactory/Unsatisfactory options: Class attendance and participation

Letter grade option: Class attendance and participation plus term paper

(Grades will be assigned solely by OSU faculty.)  

(3 hours) Call number 04378-7 for ChemPhys 880 (S/U option)