an acoustic demonstration model for cw and pulsed spectroscopy experiments torben starck, heinrich...
TRANSCRIPT
![Page 1: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/1.jpg)
An Acoustic Demonstration Model for
CW and Pulsed Spectroscopy Experiments
Torben Starck, Heinrich Mäder
Institut für Physikalische Chemie
Christian-Albrechts-Universität zu Kiel, Germany
1
Trevor Trueman, Wolfgang Jäger
Department of Chemistry
University of Alberta, Edmonton, Canada
OSU International Symposium on Molecular Spectroscopy, 64th meeting 2009, Paper RH01
![Page 2: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/2.jpg)
2
Overview
• Introduction
Principles of CW and pulsed (FT) spectroscopy experiments
Some remarks on the history of CW- and FT-MW spectroscopy
• An acoustic demonstration model
The sweep absorption experiment (CW spectroscopy)
The emission experiment (FT spectroscopy)
![Page 3: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/3.jpg)
3
CW- vs. FT-techniques
CW: continuous wave excitation
: slowly varying
sample
FT: pulsed excitation
: fixed
sample
() : absorption signal
S(t) : emission signal
t
Fourier transformation (FT)
![Page 4: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/4.jpg)
4
Spectroscopic applications
• CW- and FT-NMR spectroscopySample : molecules containing nuclei with spin > 0
Radiation frequency : RF (several 100 MHz)
Type of interaction : magnetic-dipole interaction
Sample response : macroscopic magnetic dipole moment (FID)
• CW- and FT-MW spectroscopySample : polar molecules in a static gas or a supersonic beam
Radiation frequency : MW (GHz to THz)
Type of interaction : electric-dipole interaction
Sample response : macroscopic electric dipole moment (transient emission)
For NMR and MW spectroscopy, FT-techniques hold considerable advantagesin both resolution and sensitivity over CW-techniques.
![Page 5: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/5.jpg)
5
MW spectroscopy: some remarks on its history
CW-techniques (sweep absorption experiments):
In the first thirty years of microwave spectroscopy, starting after World War II, rotational spectra of polar molecules were recorded only as absorption spectra, employing powerful modulation techniques, such as Stark-modulation (Hughes and Wilson, 1947). Further important developments of absorption spectrometers were particularly achieved in the mm- and sub-mm wavelength range, e.g. the FASSST spectrometer (de Lucia et al., 1997).
Initially, spontaneous emission signals were not considered to be strong enough to be usable for spectroscopic applications. Even in a modern textbook on Molecular Physics (2004), one can find the sentence :The rotational spectra of molecules are observed almost exclusively as absorption spectra, because the emission probability is very small as a result of low transition frequencies.This argument is based on the ν3-dependence of (incoherent) spontaneous emission probability.
![Page 6: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/6.jpg)
6
MW spectroscopy: some remarks on its history
• Early work on pulse techniques in MW spectroscopy Dicke and Romer (1955)
• Stark switching techniques Harrington (1968), Macke et al. (1972), Brittain et al. (1973), Flygare et al. (1974)
• First demonstration of FTMW spectroscopy McGurk, Mäder, Hofmann, Schmalz and Flygare (1974)
• Pulse-induced waveguide (WG)-FTMW- spectroscopy Ekkers and Flygare (1976)
• Molecular beam (MB)-FTMW- spectroscopy Balle and Flygare (1981)
FT-techniques (emission experiments) :The pulse-induced emission experiments are based on coherent spontaneous emission of the molecular sample, originating from a macroscopic polarization.
• Broadband chirped pulse (CP)-FTMW- spectroscopy Pate et al. (2005)
![Page 7: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/7.jpg)
7
FTMW spectroscopy: some remarks on its history
First demonstration of FTMW spectroscopy:
J. Chem. Phys. 61 , 3759 (1974)
Referee's comment :
J,K
3,3
2,1
3,1
4,1
![Page 8: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/8.jpg)
8
FTMW spectroscopy: laboratories all over the world
... and more than 2000 papers published
![Page 9: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/9.jpg)
9
The acoustic demonstration model
Schematic:
CW- and FT-acoustic spectroscopy
Sample : any acoustically resonant object, e.g. a tuning fork Sound waves, generated by a speaker : 20 Hz to 20 kHzType of interaction : excitation of object’s natural frequencies of vibrationSample response : mechanical vibrations of the objectDetector : microphone
In our experimental setup, the speaker and the microphone are both controlled by a computer sound card and the whole setup is housed in a plexiglass box, which serves as resonator.
![Page 10: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/10.jpg)
10
The acoustic demontration model
Experimental setup
![Page 11: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/11.jpg)
11
The sweep absorption (CW) experiment
Screen display at start of experiment
![Page 12: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/12.jpg)
12
The sweep absorption (CW) experiment
Frequency sweep without sample (background spectrum)
![Page 13: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/13.jpg)
13
The sweep absorption (CW) experiment
![Page 14: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/14.jpg)
14
The sweep absorption (CW) expermient
Frequency sweep with beer glass
![Page 15: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/15.jpg)
15
The sweep absorption (CW) experiment
Result for empty beer glass
![Page 16: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/16.jpg)
16
The pulsed emission (FT) experiment
Screen display at start of experiment
![Page 17: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/17.jpg)
17
The pulsed emission (FT) experiment
Realignment of the setup
![Page 18: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/18.jpg)
18
The pulsed emission (FT) experiment
Pulse excitation experiments with different pulse carrier frequencies
![Page 19: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/19.jpg)
19
The pulsed emission (FT) experiment
Screen shots, showing results for different pulse lengths
80 ms
t
200 ms
tpulse spectrum
sample spectrum
![Page 20: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/20.jpg)
20
The pulsed emission (FT) experiment
Screen shots, showing results for different recording times
t3 s
t1 s
Time domain signal
Spectrum
![Page 21: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/21.jpg)
21
The pulsed (FT) experiment: "beer resonances"
![Page 22: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/22.jpg)
22
The pulsed (FT) experiment: "beer resonances"
![Page 23: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/23.jpg)
23
The pulsed (FT) experiment: "beer resonances"
![Page 24: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/24.jpg)
24
The pulsed (FT) experiment: "testing beer content"
![Page 25: An Acoustic Demonstration Model for CW and Pulsed Spectroscopy Experiments Torben Starck, Heinrich Mäder Institut für Physikalische Chemie Christian-Albrechts-Universität](https://reader034.vdocuments.mx/reader034/viewer/2022051116/56649e455503460f94b3abbf/html5/thumbnails/25.jpg)
25
Danke ! Thanks !
- to the workshops
of the Institut für Physikalische Chemie
at the University of Kiel and
of the Chemistry Departmentat the University of Alberta
- for funds
from the Land Schleswig-Holstein and
from the Natural Sciences and Engineering Research Council
of Canada