Thermal Lens in Cryogenic Solutions:Thermal Lens in Cryogenic Solutions:

Vibrational overtone spectra of Vibrational overtone spectra of benzene in liquid ethanebenzene in liquid ethane

Helena Diez-y-RiegaHelena Diez-y-Riega and Carlos E. Manzanares and Carlos E. ManzanaresDepartment of Chemistry and BiochemistryDepartment of Chemistry and Biochemistry

Baylor UniversityBaylor University

Image Credit: NASA/JPL/Space Science Institute

N2 90% (78%)CH4 10%

(1.7ppm)

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.

This north polar image of Titan was acquired by Cassini’s radar instrument on May 12, 2007.

Credit: NASA/JPL

The liquid most likely a combination of methane and ethane, appears very dark to the radar instrument

Laboratory simulation : the lakes of Titan

Low temperature (90 -120 K)

Low concentration of unsaturated hydrocarbons

1. Solubility of benzene in liquid CH4, C2H6, N2 and Ar

2. Absorption spectra of benzene dissolved in liquid ethane and methane

Measuring the solubilityMeasuring the solubility

VARIAN / CARY 50 Bio UV-Vis Spectrophotometer 190nm-1100nm)

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

Thermal lensing:Thermal lensing:C-H C-H =6 vibrational overtone of benzene=6 vibrational overtone of benzene

16481 cm16481 cm-1-1

H

H

H H

H

H

COAXIAL CONFIGURATIONCOAXIAL CONFIGURATIONExperimental setupExperimental setup

A. Lopez-Calvo and C. E. Manzanares J. Phys. Chem. A, 110 (35), 10427 -10434

Pass step

cutIo

It

Pump beam

Probe beam

TLS I II

t0

0

Thermal Lens Thermal Lens C-H C-H =6 vibrational =6 vibrational overtoneovertone

benzene in CClbenzene in CCl44 at 298K at 298K

Emax=16450 cm-1

Emax=16450 cm-1

Emax=16471 cm-1

ppm

TLS

(arb

. uni

ts)

Thermal LensThermal Lens C-H C-H =6 vibrational overtone=6 vibrational overtone benzene 2% in hexane at 298K, Pbenzene 2% in hexane at 298K, Pexex=120mW=120mW

Emax = 16431 cm-1TLS

(arb

. uni

ts)

Liquid ethane 99% at 100 K*

*A. Lopez-Calvo and C. E. Manzanares: J. Phys. Chem. A 2008, 112, 1730-1740

Liquid benzene 99.99% at 298 K

Thermal LensThermal Lens

Thermal LensThermal Lens C-H C-H =6 vibrational overtone=6 vibrational overtone benzene 58 ppm in liquid ethane at 120K, benzene 58 ppm in liquid ethane at 120K,

PPexex= 220mW= 220mW

Emax=16498 cm-1

TLS

(au)

Thermal LensThermal Lens C-H C-H =6 vibrational overtone=6 vibrational overtone benzene in liquid ethane, Pbenzene in liquid ethane, Pexex= 600mW= 600mW

Emax=16467 cm-1

Emax=16498 cm-1

Torrppm,

Torr ppm,

TLS

(au)

TLS

(au)

V = 6

(600 nm)

(355 nm)

(223 nm)

SummarySummary The solubility of benzene in liquid ethane has been

measured using UV spectroscopy:

C-H =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 76132 145162 156

SummarySummary

The weak =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.

Dr. C. E. Manzanares

Dr. Alfredo Lopez-CalvoYasnahir Perez-Delgado

Nicholas HernandezDavid CamejoJenny Barroso

Robert A. Welch FoundationBaylor University

AcknowledgementAcknowledgement