Advanced Undergraduate Laboratory Course PHY442/542

Transcription

1 Advanced Undergraduate Laboratory Course PHY442/542 Burcin Bayram Department of Physics Miami University Oxford, Ohio Originally supported by: NSF-ILI, NSF, MU College of Arts and Science, & Department of Physics and originally initiated by Dr. Marcum.

2 Advanced Spectroscopy Lab: PHY442/542 GOAL: Spectroscopy of Atoms and Molecules The spectroscopy laboratory makes a unique contribution to our curriculum. Students observe atomic and molecular spectra and are then challenged to understand how the spectra relate to the structures of the associated atoms or molecules. A common student reaction to the course is that it makes quantum mechanics real, a statement that indicates that our goal has been attained. Establish an understanding of the fundamental connections between atomic and molecular spectra and the underlying structures that give rise to such spectra. Educate and motivate the laboratory and analytical skills of the students through practice, well designed standard experiments, and encouragement of creativity and originality. Introduce a wide variety of spectroscopic techniques. Employ state-of-the-art equipment. Use a guided discovery approach. Develop the student s ability to express and communicate coherently their scientific findings.

3 J. Blue, S.B. Bayram, D. Marcum, " Creating, implementing, and sustaining an advanced optical spectroscopy laboratory course", American Journal of Physics 78, (2010).

4 Advanced Spectroscopy Lab: PHY442/542 Course Syllabus (partial) Text (optional): Atomic Spectra & Atomic Structure G. Herzberg Resources: Supplements will be supplied via handouts from: -Spectra of Diatomic Molecules- G. Herzberg -Atomic and Molecular Spectroscopy- S.Svanberg -Optics- E. Hecht -Introduction to Modern Optics- G.R. Fowles - Miscellaneous handouts from a wide variety of texts, journal articles etc. -Lab handouts will be supplied by your instructor. Goals: Spectroscopic techniques are powerful tools for determining both structural and quantitative changes in organic and inorganic compounds. The reason spectroscopic techniques can ascertain the structure of compounds is because different structures absorb energies at specific frequencies or wavelengths. In other words, absorbed energy is quantized by having discrete energy levels and is specific to the particular structure. This intensity is a measure for determining whether the electronic, vibrational, or rotational transition is allowed. These concepts and techniques will be discussed in this course. Outline of the goals: (i) Introduce you to a wide variety of spectroscopic tool and techniques and hands-on experience using various light sources and lasers such as continuous wave (cw) and pulsed lasers, (ii) Study selected applications of spectroscopy, (iii) Establish understanding of some of the more fundamental connections between atomic and molecular spectra and the underlying structures that give rise to such spectra, (iv) Understand the interaction of electromagnetic radiation with matter, (v) Develop professional scientific and technical writing, (vi) Improving effective professional oral presentation skills. Grading Policy: Quizzes: 20% (in class, take-home) Lab write-ups: 60% Presentation: 20% Exams: None Grades for this course will be based on lab write-ups, quizzes and a project presentation. Class attendance is mandatory. If you have to miss a class you should inform your instructor.

5 Lab Report Information I encourage students to write lab reports using LaTeX, highquality typesetting to create professional scientific and technical documents (such as thesis, journal papers, reports, etc.). Besides this course, I have been providing LaTeX workshop to many graduate & undergraduate students in the Department of Physics at Miami.

6 Atomic Spectra Experiments Blackbody radiation, atomic and molecular spectra D-H isotope shift and Balmer series of hydrogen Fine structure splitting of alkali metals (LS Coupling) Zeeman effect in atomic sodium or cadmium light source Molecular Spectra Raman scattering spectroscopy of liquid nitrogen Vibrational structure of nitrogen molecules Vibrational spectroscopy: Laser induced fluorescence spectrum of diatomic iodine Rotational spectra of N+ 2 Other Experiments Related to Optics Make a dye laser from the construction of laser cavity from Littman-Metcalf configuration Resonance excitation of Na and Na 2 vapor Lifetime measurement of D2 line of sodium Beam profile to measure Electric Field Optical rotation using wave plates

7 Advanced Spectroscopy Lab: PHY442/542 Alkalis: spin-orbit splitting & related topics Vibrational structure of diatomics (N 2 and I 2 ) Rotational structure of diatomic (N 2 )

8 Robust Light Sources Inexpensive AC capillary discharge tubes are available for H, D, Hg, the noble gases, N 2, O 2, CO 2, halogens (~ $25 each, D is a bit more). Very robust OSRAM lamps are available for the alkalis, Hg, Cd, He, Ar (expensive). Osram Na $

9 Atomic Spectroscopy Spin-orbit interaction setup Na K Rb Bright source setup is easy. Cs

10 Cs principal series: orbital B vs n

11 L-S Coupling Selection Rule L-S coupling selection rules are obeyed, and predictions of intensity ratios within doublets (using statistical weights and the sum rule) is verified. A.A. Radzig and B.M. Smirnov Reference Data on Atoms, Molecules, and Ions Springer-Verlag

12 Molecules: additional vibrational & rotational degrees of freedom The complexity of typical molecular spectra can be quite daunting. My solution is to selectively excite particular electronic bands using a commercial N 2 AC capillary discharge (has some noble gas). Makes use of energy pooling in noble gas metastable levels as in the He-Ne laser. View the plasma near the cathode.

13 Raman Scattering Spectroscopy Nd:YAG 532 nm Pulsed laser Liquid nitrogen Dewar A spectrometer+fiber+pc Highly Visual Experiment B.L. Sands, M.J. Welsh, S. Kin, R. Marhatta, J.D. Hinkle, and S.B. Bayram, Raman Scattering spectroscopy of liquid nitrogen molecules: An advanced undergraduate physics laboratory experiment", American Journal of Physics 75, (2007).

14 Raman Scattering Spectroscopy xamples from a student s report: λ (nm) Intensity E (ev) 2'nd Anti-Stokes shifted scattering 'st Anti-Stokes shifted scattering Rayleigh Scattering 'st Stokes shifted scattering 'nd Stokes shifted scattering 'rd Stokes shifted scattering

15 Vibrational Spectroscopy of N 2 Electron impact excitation of the argon gas is the primary excitation mechanism. Metastable states of Ar at ev or ev. Spectrum of Molecular Nitrogen, A. Lofthus and P.H. Krupenie, Journal of Physical and Chemical Reference Data, 1977, vol. 6, no.1, pages S.B. Bayram and M.V. Freamat, "Vibrational spectra of N 2 : An advanced undergraduate laboratory in atomic and molecular spectroscopy", American Journal of Physics, vol. 80, pg (2012).

16 Vibrational Spectroscopy of N 2 S.B. Bayram and M.V. Freamat, "Vibrational spectra of N 2 : An advanced undergraduate laboratory in atomic and molecular spectroscopy", American Journal of Physics, vol. 80, pg (2012).

17 S.B. Bayram, M. Freamat and P.T. Arndt, "Rotational Spectra of N + 2: An Undergraduate laboratory in atomic and molecular spectroscopy", American Journal of Physics, vol. 83, pg. 867 (2015). Rotational Spectra of N 2 + Electron impact excitation of the helium gas is the primary excitation mechanism. There are other gases but the great majority of the targets for electron impact excitation collisions are predominantly helium atoms. Some direct electron impact excitation of nitrogen molecules will occur, but the frequency of such reactions will be at least an order of magnitude lower than for such electron-he atom collisions. Helium has metastable states at 19.8 & 20.6 ev. Helium metastable states have energies that are essentially resonant with the B-state in the nitrogen molecular ion N 2 +. Efficient population of the B electronic level in nitrogen will proceed by the reaction, He*(M) + N 2 (X, v = 0, various J's) N 2 + (B, primarily v' = 0, various J's) + He + e followed by a spontaneous emission via, N 2 + (B, v' = 0, J') N 2 + (X, v" = 0, J") + h

18 Rotational Spectra of N 2 + Extractable structure information:

19 Laser Induced Fluorescence in diatomic iodine Room temperature iodine cell Spectrometer Fiber and PC Vibrational Spectroscopy of I 2 S.B. Bayram and M.V. Freamat, Spectral Analysis of Laser Induced Fluorescence", 2015 BFY Proceedings, pg (2015).

20 Laser Induced Fluorescence in diatomic iodine Room temperature iodine cell Spectrometer PC Vibrational Structure of I 2 S.B. Bayram and M.V. Freamat, Spectral Analysis of Laser Induced Fluorescence", 2015 BFY Proceedings, pg (2015).

21 Student Tasks:

22 Advanced Laboratory Physics Association (ALPhA) Laboratory Immersions in 2012: My workshop attendee has produced an excellent spectrum with his students after returning back to his college. Birge-Sponer plot

23 Sample Quiz

24 Zeeman Effect in Sodium The Zeeman structure is not fully resolved. Either need better resolution, or more field...

25 Advanced Spectroscopy Lab: PHY442/542 Students Gain Experiential Learning Critical Thinking Scientific and Technical Writing Oral Presentation Experience Peer Review Experience

26 Advanced Spectroscopy Lab: PHY442/542 Assessment Scientific Writing Rubric Peer Review Rubric Quizzes Oral Presentation Rubric

27 Developed by Drs. S.B. Bayram and M. Freamat for student-student peer review.

28 Advanced Spectroscopy Lab: PHY442/542 How to use active verbs in lab reports

29 Advanced Spectroscopy Lab: PHY442/542 Techniques Fluorescence analysis using a photomultiplier tube (PMT) Fluorescence analysis using CCD Vibrational spectroscopy by electron impact excitation Vibrational spectroscopy by laser induced fluorescence Raman scattering spectroscopy Zeeman resolved polarization spectroscopy Laser excitation to study lifetime of Na atoms High and medium resolution spectrograph Rotational spectroscopy Various pulsed and cw laser spectroscopies

30 Ocean Optics Spectrometers The Most Popular Miniature Spectrometer The USB2000+VIS-NIR is a miniature spectrometer pre-configured for general visible and near-ir measurements. Covering from 350 to 1000 nm range. Using the modular approach, you can customize your absorbance and reflectance measurements with our wide array of sampling accessories and light sources. The USB Series comprises USB2000+ and USB4000 models. The models are available in custom configured and preconfigured options. Applications: Agricultural Measurements and Monitoring Biotechnology Applications Food & Beverage Quality Control Medical Diagnostics Metallurgical Analysis Polymer Analysis Protein & Nucleic Acid Analysis Teaching Labs

31 What else to integrate into the course using Ocean Optics Spectrometers? USB-ISS series integrated cuvette holder-light source accessories for USB2000+ and USB4000 spectrometers accommodate 1 cm path length cuvettes and are ideal for creating monolithic spectrophotometers from Ocean Optics components. The USB-ISS-UV-VIS-2 covers UV- Vis and Shortwave NIR wavelengths ( nm) and the USB-ISS-VIS covers Vis-Shortwave NIR wavelengths ( nm). It uses either deuterium-tungsten or tungsten-violet LEDs. $1,970.00

32 Educational Experiments Available:

33 Educational Experiments from OceanOptics