Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR,...

25
Anupam Misra HIGP, University of Hawaii, Honolulu, USA Spectroscopy: Lecture 2 Atomic Spectra www.soest.hawaii.edu\~zinin GG 711: Advanced Techniques in Geophysics and Materials Science

Transcript of Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR,...

Page 1: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

Anupam MisraHIGP, University of Hawaii, Honolulu, USA

Spectroscopy: Lecture 2

Atomic Spectra

www.soest.hawaii.edu\~zinin

GG 711: Advanced Techniques in Geophysics and Materials Science

Page 2: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

Atomic Spectra

• Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..)

• Emission spectra(Calibration lamps Ne, Hg, flames, explosion, sun, stars, LIBS: Laser induced breakdown spectroscopy)

Page 3: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

Flame tests

Page 4: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

http://www.nasa.gov/mission_pages/messenger/multimedia/mercury_telecon_20081029.html

Example sodium and calcium emissions detected by the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument on the MESSENGER spacecraft during the second Mercury flyby.

Page 5: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

Emission spectra of atoms

Page 6: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

Atomic spectra:

* Why so many lines: it has only 1 electron ?

* Simplest atom is Hydrogen atom

www.solarobserving.com/halpha.htm

Absorption spectra

Emmision spectra

Page 7: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

Bohr’s model of atom;

1. Every atom consists of nucleus and electrons revolved around the nucleus in circular orbits.

2. Electrons revolved only in certain non-radiating orbits called stationery orbits for which the total angular momentum is an integral multiple of h/2π where h is plank's constant.

L is the Angular momentum of the revolving electrons.

L = r x p = r x mV

= mvr sin 90 = mvr = n h/2π

3. Radiation occurs when an electron jumps from one permitted orbit to another. It is emitted when electron jumps from higher orbit to a lower orbit

i.e., E2 - E1 = hf, where f is frequency of radiation.

Postulates:

Page 8: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

De Broglie wave

2 π r = n λ

= n h/ (mv)

mv r = n ħ

p = h / λ = ħk k = 2 π/ λ

Page 9: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

k = 1/ (4 πεo) = 9 x 109 Nm2/C2

Page 10: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

Bohr Radius

r ∝ n2

Bohr Radius.

Page 11: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,
Page 12: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

J

Page 13: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

www.physics.udel.edu/.../images/hydrogen.gif

www.physics.fsu.edu/.../images/hydrogen.gif

Hydrogen energy levels:

-13.6 eV

0 eV

Q 1: Line C observed at 656.3 nm in Fraunhofer lines correspond to Hydrogen. Identify this transition.Q 2. Can we see the Lyman series transition n = 2 to n = 1 with our eye?

Page 14: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

1 eV = 1.6×10−19 Joulesh = 6.6×10−34 Joules.secc = 3×108 m/s = 299 792 457 m/s

E = h νc = λ ν

Photon energy E, frequency ν, wavelength λ,

532 nm (green light) corresponds to 2.33 eV.

1 eV corresponds to 1240 nm (infra red)

13.6 eV would corresponds to 91 nm (deep UV)

Bohr model: The energy of the n-th level is:

Page 15: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

* Simplest atom is Hydrogen atom

En

Page 16: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

n = 1, 2, 3, ...., denoting energy;

l = 0, 1, ..., n-1, denoting angular momentum;

m = -l, ...., l, denoting orientation (the "magnetic quantum number"),

s = -1/2, 1/2, denoting spin (m s is also used in place of s).

s, p ,d , f…for l = 0, 1, 2, 3…

K, L, M, N…for n = 1, 2, 3, 4, …

Kα line is transition from n = 2 to n = 1 (L to K level)Kβ line is transition from n = 3 to n = 1 (M to K level)

Page 17: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,
Page 18: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,
Page 19: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

http://www.flickr.com/photos/clementi/3278124162/

Page 20: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

E = ħ ω = h f

formulae to remember

p = ħ k = h / λ

c = f λ E = pc (for photon)

ω = 2 π f

k = 2 π / λ

Page 21: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

NIST Atomic Spectra Database Lines Data

Page 22: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

NIST Atomic Spectra Database Lines Data

Page 23: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

NIST Atomic Spectra Database Lines Data

Page 24: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

Homework:

Q1. Calculate the frequency and wavelength of the photon emitted when anelectron of 20 keV is brought to rest in one collision with a heavy nucleus.(x-ray production).

Q2. Find the maximum wavelength of the photon that will separate a molecule whose binding energy is 15 eV.

Q3. A 93.1 MHz radio station of 200 kW output generates how many photons in 1 minute?

Q4. Find the energy and wavelength of two photons that are produced when annihilation occurs between an electron and positron that are initially at rest.

Page 25: Spectroscopy: Lecture 2 - SOEST€¦ · Atomic Spectra • Absorption spectroscopy (UV-VIS, IR, Fraunhofer lines, atmospheric studies,..) • Emission spectra (Calibration lamps Ne,

From Wikipedia: Wave vector k