1. AMANDA L. STEBER, MARIYAM FATIMA, CRISTÓBAL PÉREZ, and MELANIE SCHNELL
AN GHz SEGMENTED CHIRPED PULSE FOURIER TRANSFORM MICROWAVE SPECTROMETER FOR ASTROCHEMICAL APPLICATIONS
AMANDA L. STEBER, MARIYAM FATIMA, CRISTÓBAL PÉREZ, and MELANIE SCHNELL
Styling: MPSD color:

2. Introduction Chirped pulse Fourier transform microwave spectroscopy
Increased data throughput
Used in both a large and small bandwidth configuration
Segmented Chirped pulse
Introduced in 2013
Used at mmw frequencies
Utilizes lower cost components
Introduces real time averaging
Goals:
Decrease the cost
Decrease acquisition times
G.G. Brown et al., J. Mol. Spectro, 238, 200 (2006)
J.L. Neill et al., Opt. Express, 21, (2013)

3. Instrumentation
N.A. Seifert et al., J. Mol. Spectro., 312, 13 (2015)

4. Instrumentation

5. Segmented, Fast Frame Chirped Pulse
Divide 8 GHz bandwidth into 10 – 800 MHz segments
Pulse train
Depending upon the pumping speed you can fit multiple segments into one gas pulse

6. Phase Stability
We are able to collect the pulses (that have been heavily attenuated by the switch)

7. Phase stability

8. OCS / Sensitivity 0.2 % OCS in Neon 3 bar backing pressure
200,000 averages
18O13CS SNR ~3:1 %
Not intensity calibrated

9. 1-Hexanal
0.2% 1-Hexanal in Neon
1 bar backing pressure
1 nozzle

10. 1-Hexanal
N.A. Seifert et al., J. Mol. Spectro., 312, 13 (2015)

11. Spurious Signals Generated from the local oscillator Occur ~200 MHz
2M average spectrum

12. 1-Hexanal Spurious SIgnals
N.A. Seifert et al., J. Mol. Spectro., 312, 13 (2015)

13. Comparison between two approaches
Broadband
Segmented
Effective Rep Rate
30 Hz
15 Hz
Power/GHz
5 W/GHz
5-7 W/GHz
Bandwidth
8 GHz /segment
800 MHz/segment
Nozzles 3 1
Pulse Duration
1 ms
2 ms
FID duration
10 ms
LNA
48 dBm
45 dBm
~ Cost
~350,000 €
~150,000 €
SNR of conformer 1 of 1-Hexanal
3500:1
~1300:1

14. Astrochemistry Applications
Broadband reaction screening
Based on the work done at Uva
Discharge nozzle
Paired with the W-band instrument
Astrochemically relevant molecules
Alaninol
Isoleucinol
M.C. McCarthy et al., Astrophys. J. Suppl. Ser., 129, 129 (2000)
D.P. Zaleski et al., Astrophys. J. Lett., 765, L10 (2013)
R. A. Loomis et al., Astrophys. J. Lett., 765, L9 (2013)

15. Conclusions and Future Directions
A new segmented, fast frame chirped pulse spectrometer has been built
Potential to reduce time
Reduces cost
Future Directions
Intensity calibration needs to be improved
Spurious signals better cateloged
Pumping speed improved

16. Acknowledgement
ERC
Louise Johnson Fellowship

17. Power Curve
Power loss across electronics
Frequency Dependent

18. 1-Hexanal
N.A. Seifert et al., J. Mol. Spectro., 312, 13 (2015)