ATOM& Molecules

Atoms & Molecules Typically Used in Our Experiments

High-Sensitive & High-Resolution

Nonlinear Laser Spectroscopy

Bread-and-butter used in our experiments are Alkali atoms viz. Rubidium (Rb) and Cesium (Cs) and triatomic molecules. Hyperfine transitions of these alkali atoms are accessed with narrow-band tunable cw diode lasers (Using Diode Lasers for Atomic Physics- C. E. Wieman and L. Hollberg, Rev. Sci. Instrum. 62, 1-20 (1991)). Raman cross-section of vibrational and rotational states in molecules have much weaker strength than electronic states in the atoms. Therefore, in our nonlinear spectroscopy experiment vibrational and rotational states in the Fermi-resonance region of molecules are accessed with narrow-band tunable pulsed lasers, which can deliver much higher peak power than can be achieved with cw lasers. Further, precision measurement technique for pulsed measurement are different from cw measurements.

For Grating Stabilized Tunable Diode Lasers

Click For: (Toptica-Photonics)

Reference Data on Atoms, Molecules, & Ions

A. A. Radzig and B. M. Smirnov

Springer Series in Chemical Physics # 31 (1985).

- Alkali D Line Data

Daniel Steck

Click For-Alkali D-Line Data

NIST Atomic Spectra Database

Click For-(Atomic-Spectra)

Optical Pumping in Atoms

William Happer

Review of Modern Physics 44, 169 (1972).

DOWNLOAD: (Optical-Pumping) Pdf

Above Figure Shows Normal Modes of Vibrations in Triatomic CO2 Molecule

& Its Rotational Spectrum

Above Figure Shows High Resolution, Rotationally Resolved

Third-Order nonlinear Spectrum of CO2 Molecule, showing Q-Branch

in the Vicinity of 1285 Cm-1 (in the Fermi-Resonance region).

What is Fermi-Resonance ?

In diatomic molecules two vibrations, one from each of the two different electronic transitions, can have nearly the same energy. This accidental degeneracy is called Fermi-resonance (after Enrico Fermi who first worked on such quantum degeneracy). In polyatomic molecules such as carbon dioxide (CO2), the vibrational and rotational structure is so complex and dense that two vibrations within the same electronic transition can be in accidental degeneracy and hence in Fermi resonance.

Our experiment deals with High-resolution and high sensitive nonlinear spectroscopy of vibrational and rotational transitions in the Fermi-resonance region of polyatomic molecule. Such spectroscopy require quantum limited detection sensitivity and very high frequency resolution. This research also deals with experimental development of pulsed precision measurement technique.

Click For- (Fermi-Resonance)

Reference: Raman Spectra of Carbon Dioxide and its Isotopic Variants in the Fermi-Resonance Regions: Part I

H. Finsterholz, H. W. Klockner, K. Srinivasan, H. W. Schrotter, and J. Brandmuller,

J. Pure Appl. Phys. 16, 370-375 (1978).

END

Appendix

1-PUB-AMO Pdf

2-PUB-AMO Pdf

3-PUB-AMO Pdf

4-PUB-AMO Pdf

5-PUB-AMO Pdf

6-BH-AMO Pdf