Microwave Spectroscopy Wave length ~ 1 cm to 100  m Wave number ~ 1 to 100 cm -1. Frequency ~ 3 x 10 10 to 3 x 10 12 Hz Energy ~ 10 to 1000 Joules/mole.

Slides:

Advertisements

Similar presentations

CHIRPED-PULSE FOURIER-TRANSFORM MICROWAVE SPECTROSCOPY OF THE PROTOTYPICAL C-H…π INTERACTION: THE BENZENE…ACETYLENE WEAKLY BOUND DIMER Nathan W. Ulrich,

Advertisements

METO 621 Lesson 6. Absorption by gaseous species Particles in the atmosphere are absorbers of radiation. Absorption is inherently a quantum process. A.

LINEAR MOLECULE ROTATIONAL TRANSITIONS:  J = 4  J = 3  J = 2  J = 1  J = 0.

Rotational Spectroscopy

Rotational Spectra Simplest Case: Diatomic or Linear Polyatomic molecule Rigid Rotor Model: Two nuclei joined by a weightless rod J = Rotational quantum.

Light (electromagnetic radiation or emr) Composed of photons - can be counted travels as spread out wave can interact only at single point E B E = electric.

Vibrational Spectroscopy I

P461 - Molecules 21 MOLECULAR ENERGY LEVELS Have Schrod. Eq. For H 2 (same ideas for more complicated). For proton and electron 1,2 real solution: numeric.

Rotational Spectra Simplest Case: Diatomic or Linear Polyatomic molecule Rigid Rotor Model: Two nuclei joined by a weightless rod J = Rotational quantum.

Atmospheric Spectroscopy

Introduction to Infrared Spectrometry Chap 16. Infrared Spectral Regions Table 16-1 Most used – 15.

Rotational and Vibrational Spectra

Classical Model of Rigid Rotor

Microwave Spectroscopy II

Vibrational Transitions

Rotational Spectra Simplest Case: Diatomic or Linear Polyatomic molecule Rigid Rotor Model: Two nuclei joined by a weightless rod J = Rotational quantum.

Rotational Spectroscopy Born-Oppenheimer Approximation; Nuclei move on potential defined by solving for electron energy at each set of nuclear coordinates.

(8) Absorption – Visible and IR Physics of the Atmosphere II Atmo II 193a.

Intro/Review of Quantum

Spectroscopy Microwave (Rotational) Infrared (Vibrational)

Microwave Rotational Spectroscopy

Microwave Spectroscopy Rotational Spectroscopy

Vibrational Spectroscopy

Spectroscopic Analysis Part 4 – Molecular Energy Levels and IR Spectroscopy Chulalongkorn University, Bangkok, Thailand January 2012 Dr Ron Beckett Water.

Vibrational and Rotational Spectroscopy

Vibrational Spectroscopy

5. Vibrations in Molecules

Lecture 34 Rotational spectroscopy: intensities. Rotational spectroscopy In the previous lecture, we have considered the rotational energy levels. In.

Lecture 33 Rotational spectroscopy: energies (c) So Hirata, Department of Chemistry, University of Illinois at Urbana-Champaign. This material has been.

Revisit vibrational Spectroscopy

MOLECULAR SPECTROSCOPY  SPECTROSCOPY IS THAT BRANCH OF SCIENCE WHICH DEALS WITH THE STUDY OF INTERACTION OF ELECTROMAGNETIC RADIATION WITH MATTER.  ELECTROMAGNETIC.

MOLECULAR SPECTROSCOPY  SPECTROSCOPY IS THAT BRANCH OF SCIENCE WHICH DEALS WITH THE STUDY OF INTERACTION OF ELECTROMAGNETIC RADIATION WITH MATTER.  ELECTROMAGNETIC.

1 B. RAM PRASAD, MANGALA SUNDER KRISHNAN Department of Chemistry, Indian Institute of Technology Madras, Chennai , India. AND E. ARUNAN Department.

ROTATIONAL SPECTROSCOPY

SPECTROSCOPY AND ANALYTICAL CHEMISTRY  A variety of spectroscopic techniques can be used to study/elucidate ground and excited state atomic and molecular.

Partition functions of ideal gases. We showed that if the # of available quantum states is >> N The condition is valid when Examples gases at low densities.

Ch 8. The Vibrational and Rotational Spectroscopy of Diatomic Molecules MS310 Quantum Physical Chemistry - light interacts with molecules to induce transitions.

Tutorial – 4 1) Calculate the moment of inertia (I) and bond length (r) from microwave spectrum of CO. First line (J = 0 to J=1 transition) in the rotation.

IR Spectroscopy Wave length ~ 100 mm to 1 mm

Lecture 33 Rotational spectroscopy: energies. Rotational spectroscopy In this lecture, we will consider the rotational energy levels. In the next lecture,

The Ideal Diatomic and Polyatomic Gases. Canonical partition function for ideal diatomic gas Consider a system of N non-interacting identical molecules:

Lecture 34 Rotational spectroscopy: intensities (c) So Hirata, Department of Chemistry, University of Illinois at Urbana-Champaign. This material has been.

Schrödinger Equation – Model Systems: We have carefully considered the development of the Schrödinger equation for important model systems – the one, two.

Infrared Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers (nm) to 1 mm. NameWavelength Gamma rayless than.

CHM 321:PHYSICAL CHEMISTRY II SPECTROSCOPY. WHAT IS SPECTROSCOPY? ORIGINATED FROM THE STUDY OF VISSIBLE LIGHT DISPERSED ACCORDING TO WAVELENGTH OR INTERACTION.

IR Spectroscopy CHM 411 Suroviec. I. Theory of IR Spectroscopy Frequency of absorbed radiation is the molecular vibration frequency responsible for absorption.

Lecture from Quantum Mechanics. Marek Zrałek Field Theory and Particle Physics Department. Silesian University Lecture 5.

RAMAN SPECTROSCOPY THREE EFFECTS OF RADIATION OF LIGHT ON MOLECULES CAN OCCUR. (i) RADIATION OF LIGHT ON TO MOLECULES, SOME OF THE LIGHT WILL BE REFLECTED.

Raman Spectroscopy BY Dr. Bhawna.

Molecular Spectroscopy

Spectroscopy Microwave (Rotational) Infrared (Vibrational)

Infrared Spectroscopy

Molecular Spectroscopy

UNIT IV Molecules.

Diatomic molecules

Microwave Spectrometer

Which of the molecules below is a prolate symmetric top?

Which of the molecules below is a prolate symmetric top?

Microwave Spectroscopy Rotational Spectroscopy

Rigid Diatomic molecule

This is the far infra red spectrum of the diatomic molecule CO

I = μr2 μ = m1m2/(m1+m2) I (uÅ2) = / B(cm-1)

6. Vibrational Spectroscopy

Molecular Spectra By – P.V.Koshti.

How do you calculate the moment of inertia of a polyatomic molecule

Harmonic Oscillator.

How do I get experimental information on bond lengths in simple

Rotational Energy Levels for rigid rotor: Where Rotational Spectra of Rigid Diatomic molecule. BY G JANAKIRAMAN EGS A&S COLLAGE

Vibrational Energy Levels

The Rigid Rotor.

Presentation transcript:

Microwave Spectroscopy Wave length ~ 1 cm to 100  m Wave number ~ 1 to 100 cm -1. Frequency ~ 3 x to 3 x Hz Energy ~ 10 to 1000 Joules/mole Spectrum of CO cm -1 Equally spaced lines

Rotation of a diatomic molecule R r1r1 r2r2 m2m2 m1m1

Equivalent to that of a single particle

The Rigid Rotor

(2J+1) fold degeneracy! B 6B 2B 0 3 JEJEJ

Electric field + diatomic molecule

Must have a permanent dipole moment Selection Rules Z -part Initial state Final state Transition Moment = Integral

X -part Y -part

J J 6B 2B 0 Blue –ALLOWED Red – NOT

J B 6B 2B 0 EJEJ 4B6B8B Equally spaced lines!

Intensities 2B4B6B8B 10B 12B 14B 16B Why does the intensities increase and then decrease? Depends on initial populations!

Population of levels If B=2 cm -1 then

Isotope Effect

Non-Rigid Rotor

Polyatomics 1. Linear Molecules – similar to diatomics Three moments of Inertia! 16 O 12 C 32 S - B = 6, MHz 16 O 12 C 33 S - B = 6, MHz 16 O 12 C 34 S - B = 5, MHz (from: Graybeal)

2. Non-Linear Molecules

a) Spherical Top Examples: CH 4, SF 6 etc Do not absorb Microwave Radiation!

b) Symmetric Top BCl 3 CH 3 F

Prolate CH 3 F

Oblate BCl 3

a) Asymmetric Top No simple expression for Allowed energy levels

Pulsed nozzle FTMW spectrometer

Benzene dimer, c.m-c.m distance 4.96Å Distance very close to what is found in crystal! Arunan and Gutowsky J. Chem. Phys. 98, 4294 (1993)