Frontiers in Spectroscopy

Chemical Physics 880.01 and 880.02

Winter 2012

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 (for students 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.

All readings and lecture notes will be kept current on Carmen. If you were enrolled for Frontiers this quarter, you have your normal student login and password. If you are an advisor or post-doc and would like access to the readings and notes, email Becky Gregory, gregory.10@osu.edu, and she will arrange for a login and password for this site.

List of speakers and dates scheduled:

January 10 - 5:30pm-6:30pm in 2015 McPherson Lab - Pre-Lecture discussion by Brenda Winnewisser
Readings:
McCarthy, Gottlieb, Gupta, Thaddeus paper
Herbst and Klemperer paper
Thaddeus and McCarthy paper

January 11-13 Michael McCarthy - Harvard Smithsonian

• Lecture 1 Molecular astrophysics and reactive molecule laboratory spectroscopy: What, When, Where, and Why?
  - Detection of atoms in interstellar gas
  - Diffuse interstellar bands
  - Simple diatomics
  - Advent of radio astronomy
  - OH, NH3 and the 'Fischer Chemical' principle
  - HCO+ and ion-molecule chemistry
  - Modern astrochemistry and applications
  - Role of laboratory spectroscopy
  
• Lecture 2 How do we detect and identify new molecules (with certainty)? A user's guide
  - Rotational spectroscopy: a sensitive, structure-based analysis tool
  - Basic principles
  - Production methods: How do we generate desired species?
  - The role of ab initio theory
  - Assignment strategies and techniques
  - Case studies: positive molecular ions; broadband screening and reaction chemistry perspective of a simple mixture
  
• Lecture 3 Detection of known or postulated astronomical molecules in the radio band
  Need for high-resolution measurements
  Rotational spectroscopy: observational factors, constraints, and challenges
  Experimental techniques
  Long path absorption
  Fourier transform methods
  - Cavity
  - Chirped broadband
  Case study: Negative molecular ions in laboratory and in space
  

Readings:
Conrad and Sanders paper
Whitney, Takami, Sanders and Okura paper
Kranendonk et al. paper

January 18-20 Scott Sanders - University of Wisconsin

• Lecture 1 (Wed morning (9 to 10:18)):
  - spectroscopic measurements in practical environments (piston & gas turbine engines, etc.)
  - example: gas thermometry in a Honda engine
  - definitions related to high-repetition-rate hyperspectral absorption spectroscopy
  - rapidly swept-wavelength lasers and high-speed grating spectrometers
  - spectroscopic databases and associated experiments
  - overview of noise considerations

• Lecture 2 (Thurs morning (9 to 10:18)):
  - selection of optimum wavelengths
  - the Fourier limit associated with linewidth and data rate
  - available hardware
  
  1. swept-wavelength lasers
  2. grating spectrometers
  3. multiplexed linelocked lasers
  4. femtosecond comb pairs
  5. multiplexed vertical-cavity surface-emitting lasers
  - managing unknown lineshapes

• Lecture 3 (Fri morning (9 to 10:18)):
  - gas property imaging by absorption tomography
  - extension to UV, mid-IR wavelengths
  - future work / outlook

Readings:
Barnes, Squires, Sibert paper
Florio, Zwier, Myshakin, Jordan, Sibert paper
Nagesh, Sibert paper

January 25-27 Edwin L. Sibert - University of Wisconsin

• Lecture 1 - Background for Theoretical Descriptions of IR Spectroscopy
  1. Choices of Coordinates
  2. Normal Modes and Anharmonicities
  3. Determining the Hamiltonian
  4. Representations - Adiabatic versus SCF
  5. Basis Sets (Normal Mode Bases versus DVR's)
  
• Lecture 2 - Perturbative and Variational Treatments of Molecular Vibrations.
  1. Davidson and Lanczos Iterative Methods for Spectra Determination
  2. Van Vleck Perturbation Theory
  3. Examples
  
• Lecture 3 - Vibrations at a conical intersection: Methoxy
  1. Conical Intersections and Vibronic Hamiltonians
  2. Dipole moment and Potential Surfaces
  3. Jahn-Teller, Spin -Orbit, and Fermi Couplings
  4. LIF, IR, and SEP Spectroscopy
  

February 29-March 2 Mark Johnson - Yale University

• Lecture 1 - Anharmonicities in ion hydration
  1. Born solvation and dielectric saturation
  2. Mechanical and electrical anharmonicities in halide ion hydration
  3. Solvent mediated Fermi intramolecular coupling
  4. Vibrationally adiabatic approach for mechanical anharmonicity: Franck-Condon factors in the vibrational manifold
  
• Lecture 2 - Hydrated electrons and protons
  1. Polarons and excess charge localization in dielectic media
  2. Size of the excess electron wavefunction from spectral moment analysis
  3. Dipole bound anions & the electron binding site
  4. Fano profiles and antenna amplification of the vibrational intensities
  5. The Zundel proton continuum and Grotthuss proton transport
  6. The intermolecular proton bond
  7. Proton-coupled covalent bond formation
  
• Lecture 3 - Recent developments: Dealing with spectral congestion in complex systems
  1. Accessing solution species using atmospheric ionization
  2. Cryogenic ion processing for linear spectroscopy through "tagging"
  3. Isomer-specific strategies using double resonance - Application to peptide conformers
  4. Isotope-edited spectroscopy for bond-specific information in host-guest complexes
  

March 7-9 Nathalie Picque - CNRS and Max Planck Institute of Quantum Optics

• Lecture 1 - Laser frequency combs
  The regular pulse train of a mode-locked femtosecond laser can give rise to a regular comb spectrum of millions of laser modes with a spacing precisely equal to the pulse repetition frequency. Laser frequency combs were conceived a decade ago as tools for the precision spectroscopy of atomic hydrogen. Through the development of optical frequency comb techniques, a set-up of the size 1x1 m2, good for precision measurements of any frequency, and even commercially available, has replaced the elaborate previous frequency-chain schemes for optical frequency measurements, which only worked for selected frequencies. A true revolution in optical frequency measurements has occurred, paving the way for the creation of all-optical clocks with a precision that might approach 10-18. A decade later, frequency combs are now common equipment in all frequency metrology-oriented laboratories. They are also becoming enabling tools for an increasing number of applications, from the calibration of astronomical spectrographs to attosecond science. In this lecture, the principles of operation and advances in the technology of optical combs will be introduced. The use of laser frequency combs in frequency metrology as well as their recent promising applications (excluding molecular spectroscopy) will be reviewed.
  Suggested readings:
  T.W. Hansch, Nobel Lecture: Passion for precision. Rev. Mod. Phys. 78, 1297-1309 (2006).
  S. Cundiff, J. Ye, J.L. Hall, Rulers of light. Scientific American, April 2008 issue, 74-81.
• Lecture 2 - Molecular spectroscopy with laser frequency combs
  Laser frequency combs have recently demonstrated an intriguing potential for dramatic advances in molecular spectroscopy. They are thus presently envisioned to bring a truly revolutionary impact to emerging or unexpected fields for many areas of research relevant to molecular science. As for precision spectroscopy of simple atomic systems, in molecular spectroscopy the comb may serve as a frequency ruler against which the frequency of a continuous-wave laser used to probe the sample is calibrated. However in recent years, novel techniques have been developed in which the comb directly interrogates the sample. Direct absorption frequency comb spectroscopy results in short measurement time and high accuracy over a broad spectral bandwidth. Such advances have been demonstrated with Michelson-based Fourier transform, dispersive and dual-comb based Fourier transform spectrometers. This lecture will present the different techniques that have been recently implemented and discuss their respective potential.
  Only a short introduction to Fourier transform spectroscopy with two laser frequency combs - dual-comb spectroscopy - will be given, as it will be the focus of the third lecture.
  Suggested readings:
  F. Adler, M. J. Thorpe, K. C. Cossel, and J. Ye, Cavity-Enhanced Direct Frequency Comb Spectroscopy: Technology and Applications, Annu. Rev. Anal. Chem. 3, 175 - 205 (2010)
  J. Mandon, G. Guelachvili, N. Picque, Fourier Transform Spectroscopy with a Laser Frequency Comb, Nature Photonics 3, 99-102, 2009.
  
• Lecture 3 - Fourier transform spectroscopy with laser frequency combs
  Recent experiments of multi-heterodyne frequency comb Fourier transform spectroscopy (also called dual-comb spectroscopy) have demonstrated that the precisely spaced spectral lines of a laser frequency comb can be harnessed for new techniques of molecular spectroscopy. Even the first proof-of-principle experiments, carried out in the near-infrared region, have demonstrated a very exciting potential of dual-comb spectroscopy without moving parts for ultra-rapid and ultra-sensitive recording of complex broad spectral bandwidth molecular spectra. Compared to conventional Michelson-based Fourier transform spectroscopy, recording times could be shortened from seconds to microseconds, with intriguing prospects for spectroscopy of short lived transient species. The resolution improves proportionally to the measurement time. Therefore longer recordings allow high resolution spectroscopy of molecules with extreme precision, since the absolute frequency of each laser comb line can be known with the accuracy of an atomic clock.
  This lecture will introduce the physical principles of dual-comb spectroscopy, and discuss the main achievements and remaining challenges associated with its implementation. Envisioned developments and their foreseen impact will be presented.
  Suggested readings:
  B. Bernhardt, A. Ozawa, P. Jacquet, M. Jacquey, Y. Kobayashi, T. Udem, R. Holzwarth, G. Guelachvili, T.W. Hansch, N. Picque, Cavity-enhanced dual-comb spectroscopy, Nature Photonics 4, 55-57, 2010.
  N. Picque, T.W. Hansch, Molecular spectroscopy with laser frequency combs, Proceedings of the 11th International Conference on Laser Spectroscopy, 7 pages, in press (2012).
  

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  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 19240 for ChemPhys 880.01 (S/U option)

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