1. Thermal Lens in Cryogenic Solutions: Vibrational overtone spectra of benzene in liquid ethane
Helena Diez-y-Riega and Carlos E. Manzanares
Department of Chemistry and Biochemistry
Baylor University

2. This natural color image shows Titan's upper atmosphere:
an active place where methane molecules are being broken apart by solar ultraviolet light . The products combine to form compounds like ethane and acetylene. N2
90% (78%)
CH4
10% (1.7ppm)
Image Credit: NASA/JPL/Space Science Institute

3. This north polar image of Titan was acquired by Cassini’s radar instrument on May 12, 2007.
The liquid most likely a combination of methane and ethane, appears very dark to the radar instrument
Credit: NASA/JPL

5. Laboratory simulation : the lakes of Titan
Low temperature ( K)
Low concentration of unsaturated hydrocarbons
Solubility of benzene in liquid CH4, C2H6, N2 and Ar
Absorption spectra of benzene dissolved in liquid ethane and methane

6. Measuring the solubility
VARIAN /
CARY 50 Bio UV-Vis Spectrophotometer (l=190nm-1100nm)

7. UV spectrum of benzene 69 ppm in liquid ethane at 102 K

9. C-H Du=6 vibrational overtone of benzene 16481 cm-1
Thermal lensing:
C-H Du=6 vibrational overtone of benzene
16481 cm-1
u=6
u=0 H

10. Experimental setup COAXIAL CONFIGURATION Pass step Pump beam cut IoIt
Pump beam
Probe beam
A. Lopez-Calvo and C. E. Manzanares
J. Phys. Chem. A, 110 (35),

11. Thermal Lens C-H Du=6 vibrational overtone benzene in CCl4 at 298K
TLS (arb. units)
DEmax=16450 cm-1 1%
DEmax=16450 cm-1
0.1%
0.01% =100ppm
DEmax=16471 cm-1

12. Thermal Lens C-H Du=6 vibrational overtone
benzene 2% in hexane at 298K, Pex=120mW
TLS (arb. units)
DEmax = cm-1

13. Thermal Lens Liquid ethane 99% at 100 K*
Liquid benzene 99.99% at 298 K
Du=6
*A. Lopez-Calvo and C. E. Manzanares: J. Phys. Chem. A 2008, 112,

14. Thermal Lens C-H Du=6 vibrational overtone
benzene 58 ppm in liquid ethane at 120K,
Pex= 220mW
DEmax=16498 cm-1
TLS (au)

15. Thermal Lens C-H Du=6 vibrational overtone
benzene in liquid ethane, Pex= 600mW
DEmax=16467 cm-1
19 Torr = 48 ppm,
100 K
TLS (au)
DEmax=16498 cm-1
19 Torr = 50 ppm,
120 K
TLS (au)

16. V = 6
(600 nm)
(355 nm)
(223 nm)

18. Summary
The solubility of benzene in liquid ethane has been measured using UV spectroscopy:
C-H Du=6 vibrational overtone spectra of solutions of benzene have been obtained
benzene in carbon tetrachloride at room temperature in concentrations as low as 100 ppm.
benzene dissolved in hexane at room temperature. This spectrum has evidenced the viability of using a saturated hydrocarbon as a solvent.
Temperature (K)
Solubility (ppm)
102 76
132
145
162
156

19. Summary
The weak Du=6 C-H vibrational overtone spectra of benzene dissolved in liquid ethane at 120K and 100K, and very low concentrations (~50 ppm) have been obtained.
We have shown that it is possible to study overtone spectra of molecules in solution at the solubility level (ppm) of cryogenic liquids.

20. Acknowledgement Dr. C. E. Manzanares Dr. Alfredo Lopez-Calvo
Yasnahir Perez-Delgado
Nicholas Hernandez
David Camejo
Jenny Barroso
Robert A. Welch Foundation
Baylor University