## Interference-free gas-phase thermometry at elevated pressure using hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering |

Optics Express, Vol. 20, Issue 5, pp. 5003-5010 (2012)

http://dx.doi.org/10.1364/OE.20.005003

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### Abstract

Rotational-level-dependent dephasing rates and nonresonant background can lead to significant uncertainties in coherent anti-Stokes Raman scattering (CARS) thermometry under high-pressure, low-temperature conditions if the gas composition is unknown. Hybrid femtosecond/picosecond rotational CARS is employed to minimize or eliminate the influence of collisions and nonresonant background for accurate, frequency-domain thermometry at elevated pressure. The ability to ignore these interferences and achieve thermometric errors of <5% is demonstrated for N_{2} and O_{2} at pressures up to 15 atm. Beyond 15 atm, the effects of collisions cannot be ignored but can be minimized using a short probe delay (~6.5 ps) after Raman excitation, thereby improving thermometric accuracy with a time- and frequency-resolved theoretical model.

© 2012 OSA

## 1. Introduction

1. S. Roy, J. R. Gord, and A. K. Patnaik, “Recent advances in coherent anti-Stokes Raman scattering spectroscopy: Fundamental developments and applications in reacting flows,” Prog. Energ. Combust. Sci. **36**(2), 280–306 (2010). [CrossRef]

2. T. Seeger, F. Beyrau, A. Brauer, and A. Leipertz, “High-pressure pure rotational CARS: comparison of temperature measurements with O_{2}, N_{2} and synthetic air,” J. Raman Spectrosc. **34**, 932–939 (2003). [CrossRef]

3. F. Vestin, M. Afzelius, and P. E. Bengtsson, “Development of rotational CARS for combustion diagnostics using a polarization approach,” Proc. Combust. Inst. **31**(1), 833–840 (2007). [CrossRef]

4. F. M. Kamga and M. G. Sceats, “Pulse-sequenced coherent anti-Stokes Raman scattering: Method for suppression of the non-resonant background,” Opt. Lett. **5**(3), 126–128 (1980). [CrossRef] [PubMed]

6. P. Beaud, H. M. Frey, T. Lang, and M. Motzkus, “Flame thermometry by femtosecond CARS,” Chem. Phys. Lett. **344**(3-4), 407–412 (2001). [CrossRef]

7. T. R. Meyer, S. Roy, and J. R. Gord, “Improving signal-to-interference ratio in rich hydrocarbon-air flames using picosecond coherent anti-Stokes Raman scattering,” Appl. Spectrosc. **61**(11), 1135–1140 (2007). [CrossRef] [PubMed]

8. T. Seeger, J. Kiefer, A. Leipertz, B. D. Patterson, C. J. Kliewer, and T. B. Settersten, “Picosecond time-resolved pure-rotational coherent anti-Stokes Raman spectroscopy for N(_{2}) thermometry,” Opt. Lett. **34**(23), 3755–3757 (2009). [CrossRef] [PubMed]

9. G. Knopp, P. Beaud, P. Radi, M. Tulej, B. Bougie, D. Cannavo, and T. Gerber, “Pressure-dependent N_{2} Q-branch fs-CARS measurements,” J. Raman Spectrosc. **33**(11-12), 861–865 (2002). [CrossRef]

10. T. Lang and M. Motzkus, “Determination of line shift coefficients with femtosecond time resolved CARS,” J. Raman Spectrosc. **31**(1-2), 65–70 (2000). [CrossRef]

11. T. Lang, M. Motzkus, H. M. Frey, and P. Beaud, “High resolution femtosecond coherent anti-Stokes Raman scattering: Determination of rotational constants, molecular anharmonicity, collisional line shifts, and temperature,” J. Chem. Phys. **115**(12), 5418–5426 (2001). [CrossRef]

12. P. Beaud and G. Knopp, “Scaling rotationally inelastic collisions with an effective angular momentum parameter,” Chem. Phys. Lett. **371**(1-2), 194–201 (2003). [CrossRef]

14. G. Knopp, P. Radi, M. Tulej, T. Gerber, and P. Beaud, “Collision induced rotational energy transfer probed by time-resolved coherent anti-Stokes Raman scattering,” J. Chem. Phys. **118**(18), 8223–8233 (2003). [CrossRef]

_{2}, N

_{2}, CO, and C

_{2}H

_{2}). Such measurements were intended to provide critical information for modeling the composition-dependent line widths of gas-phase spectra for accurate thermometry.

*a priori*, however, it is advantageous to avoid entirely the effects of collisions. Whereas previous ultrafast CARS temperature measurements exploited features of the molecular response at long delay times and, therefore, required detailed modeling of collisional effects [15

15. T. Lang and M. Motzkus, “Single-shot femtosecond coherent anti-Stokes Raman scattering thermometry,” J. Opt. Soc. Am. B **19**(2), 340–344 (2002). [CrossRef]

16. R. P. Lucht, S. Roy, T. R. Meyer, and J. R. Gord, “Femtosecond coherent anti-Stokes Raman scattering measurement of gas temperatures from frequency-spread dephasing of the Raman coherence,” Appl. Phys. Lett. **89**(25), 251112 (2006). [CrossRef]

16. R. P. Lucht, S. Roy, T. R. Meyer, and J. R. Gord, “Femtosecond coherent anti-Stokes Raman scattering measurement of gas temperatures from frequency-spread dephasing of the Raman coherence,” Appl. Phys. Lett. **89**(25), 251112 (2006). [CrossRef]

1. S. Roy, J. R. Gord, and A. K. Patnaik, “Recent advances in coherent anti-Stokes Raman scattering spectroscopy: Fundamental developments and applications in reacting flows,” Prog. Energ. Combust. Sci. **36**(2), 280–306 (2010). [CrossRef]

15. T. Lang and M. Motzkus, “Single-shot femtosecond coherent anti-Stokes Raman scattering thermometry,” J. Opt. Soc. Am. B **19**(2), 340–344 (2002). [CrossRef]

## 2. Theory and experiment

17. J. D. Miller, S. Roy, M. N. Slipchenko, J. R. Gord, and T. R. Meyer, “Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering,” Opt. Express **19**(16), 15627–15640 (2011). [CrossRef] [PubMed]

21. B. D. Prince, A. Chakraborty, B. M. Prince, and H. U. Stauffer, “Development of simultaneous frequency- and time-resolved coherent anti-Stokes Raman scattering for ultrafast detection of molecular Raman spectra,” J. Chem. Phys. **125**(4), 044502 (2006). [CrossRef] [PubMed]

*v*= 0, Δ

*J*= + 2), the molecular response from the pump (ω

_{pump}) and Stokes (ω

_{Stokes}) pulses is treated phenomenologically as a function of time,

*t*, in Eq. (1),where each transition is assigned an intensity,

*I*, a frequency (s

_{J + 2,J}^{−1}),

*ω*, and linewidth (s

_{J + 2,J}^{−1}),

*Γ*[17

_{J + 2,J}17. J. D. Miller, S. Roy, M. N. Slipchenko, J. R. Gord, and T. R. Meyer, “Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering,” Opt. Express **19**(16), 15627–15640 (2011). [CrossRef] [PubMed]

21. B. D. Prince, A. Chakraborty, B. M. Prince, and H. U. Stauffer, “Development of simultaneous frequency- and time-resolved coherent anti-Stokes Raman scattering for ultrafast detection of molecular Raman spectra,” J. Chem. Phys. **125**(4), 044502 (2006). [CrossRef] [PubMed]

*I*is not a function of time, but is highly dependent on temperature,

_{J + 2,J}*T*. The response decays exponentially with a time constant

*τ*=

_{J + 2,J}*Γ*The linewidth is highly temperature and pressure dependent, displaying a linear dependence on pressure and more complex inverse relationship with temperature [22

_{J + 2,J}^{−1}.22. L. A. Rahn and R. E. Palmer, “Studies of nitrogen self-broadening at high-temperature with inverse Raman-spectroscopy,” J. Opt. Soc. Am. B **3**(9), 1164–1169 (1986). [CrossRef]

8. T. Seeger, J. Kiefer, A. Leipertz, B. D. Patterson, C. J. Kliewer, and T. B. Settersten, “Picosecond time-resolved pure-rotational coherent anti-Stokes Raman spectroscopy for N(_{2}) thermometry,” Opt. Lett. **34**(23), 3755–3757 (2009). [CrossRef] [PubMed]

17. J. D. Miller, S. Roy, M. N. Slipchenko, J. R. Gord, and T. R. Meyer, “Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering,” Opt. Express **19**(16), 15627–15640 (2011). [CrossRef] [PubMed]

23. B. Lavorel, H. Tran, E. Hertz, O. Faucher, P. Joubert, M. Motzkus, T. Buckup, T. Lang, H. Skenderovi, G. Knopp, P. Beaud, and H. M. Frey, “Femtosecond Raman time-resolved molecular spectroscopy,” C. R. Phys. **5**, 215–229 (2004). [CrossRef]

8. T. Seeger, J. Kiefer, A. Leipertz, B. D. Patterson, C. J. Kliewer, and T. B. Settersten, “Picosecond time-resolved pure-rotational coherent anti-Stokes Raman spectroscopy for N(_{2}) thermometry,” Opt. Lett. **34**(23), 3755–3757 (2009). [CrossRef] [PubMed]

**19**(16), 15627–15640 (2011). [CrossRef] [PubMed]

_{2}and O

_{2}CARS spectra were recorded at 298 and 295 K, respectively, from 1 to 20 atm. The pure gases were pressurized in a cylindrical stainless-steel vessel, and the temperature was measured with a 1/16-inch diameter K-type thermocouple and pressure with a digital pressure gauge (0–500 ± 1.25 psi). The frequency-dispersed RCARS signal is detected using a 0.303-m spectrometer (1200 line/mm) with sufficient resolution for distinguishing individual rotational transitions. The signal can be numerically integrated over the entire S-branch (~10–200 cm

^{−1}) as given in Fig. 1 for N

_{2}and O

_{2}at pressures of 1, 2.5, 5, 10, 15, and 20 atm, or numerically integrated over a single transition.

*et al.*[2

2. T. Seeger, F. Beyrau, A. Brauer, and A. Leipertz, “High-pressure pure rotational CARS: comparison of temperature measurements with O_{2}, N_{2} and synthetic air,” J. Raman Spectrosc. **34**, 932–939 (2003). [CrossRef]

*et al.*[24

24. L. Martinsson, P. E. Bengtsson, M. Alden, S. Kroll, and J. Bonamy, “A test of different rotational Raman linewidth models: accuracy of rotational coherent anti-Stokes-Raman scattering thermometry in nitrogen from 295 to 1850 K,” J. Chem. Phys. **99**(4), 2466–2477 (1993). [CrossRef]

*J*, decreasing as

*J*is increased. Thus the low rotational states exhibit higher rates of energy transfer and decay at a faster rate than high rotational states. As highlighted in our previous publications [17

**19**(16), 15627–15640 (2011). [CrossRef] [PubMed]

20. J. D. Miller, S. Roy, J. R. Gord, and T. R. Meyer, “Communication: Time-domain measurement of high-pressure N_{2} and O_{2} self-broadened linewidths using hybrid femtosecond∕picosecond coherent anti-Stokes Raman scattering,” J. Chem. Phys. **135**(20), 201104 (2011). [CrossRef] [PubMed]

^{−1}to 0.063 cm

^{−1}from

*J*= 4 to 18 for N

_{2}, and 0.107 cm

^{−1}to 0.064 cm

^{−1}for

*N*= 5 to 23 for O

_{2}. Since each transition decays at a different rate, the RCARS spectra appear to shift to higher temperatures as the low rotational states decay rapidly with increased probe delay. The experimentally measured time decays are well predicted by the theoretical model in Fig. 1 and illustrate the short time window between nonresonant background and strong collisional dephasing at high pressure. The dephasing rate for N

_{2}is faster than that of O

_{2}, which implies that N

_{2}CARS thermometry will be more sensitive to collisions.

## 3. Results and discussion

^{−1}) [17

**19**(16), 15627–15640 (2011). [CrossRef] [PubMed]

^{−1}(4.1 ps) to achieve a minimum probe delay of 6.5 ps (~1000 × nonresonant suppression). This bandwidth is sufficient to avoid spectral overlap of the transitions so that the effects of rotational energy transfer can be clearly observed in the frequency-domain spectra. For illustration, experimental O

_{2}spectra are presented in Fig. 2 at fixed delays of (a) 6.5 and (b) 25 ps and pressures of 1 atm and 10 atm (symbols). The theoretical O

_{2}spectrum (solid lines) assumes a pressure of 1 atm. At a probe delay of 6.5 ps, shown in Fig. 2(a), the difference between the two experimental spectra is negligible, leading to best-fit temperatures that are within 4% of 295 K. This illustrates the independence from collisional effects at short probe delays. For the longer probe delay of 25 ps, as shown in Fig. 2(b), the experimental spectrum at 1 atm is nearly the same as that shown at 6.5 ps. However, for a probe delay of 25 ps and a pressure of 10 atm, the spectrum shows an apparent population shift towards higher rotational states, leading to a best-fit temperature of 342 K. This represents an error of 16%.

*a priori*, but at elevated pressure this requires that the probe pulse be shorter than and arrive sooner than 25 ps. To evaluate the potential for interference-free measurements from 1 to 20 atm, the thermometric error was investigated from a minimum probe delay of 6.5 ps (to avoid nonresonant background) to a maximum of 150 ps (typical of ps CARS with probe pulses of ~80 ps or higher). This investigation was performed by fitting the time-dependent spectra using a spectral database where the linewidth was set to zero in the molecular response function (Eq. (1)) for all rotational transitions. Best-fit temperatures are plotted as a function of probe delay in Figs. 3(a) and 4(a) . The constant solid line represents the actual temperature, and the constant dashed lines represent ± 5% error.

_{2}or O

_{2}CARS spectra at elevated pressure. At the shortest probe delay of 6.5 ps, for example, the thermometric error without corrections for nonresonant background or collisional energy transfer is <5% up to 15 atm. This error is slightly higher than that previously reported using validated RCARS models for high resolution frequency domain thermometry at elevated pressure [2

2. T. Seeger, F. Beyrau, A. Brauer, and A. Leipertz, “High-pressure pure rotational CARS: comparison of temperature measurements with O_{2}, N_{2} and synthetic air,” J. Raman Spectrosc. **34**, 932–939 (2003). [CrossRef]

25. M. Afzelius, P. E. Bengtsson, J. Bood, J. Bonamy, F. Chaussard, H. Berger, and T. Dreier, “Dual-broadband rotational CARS modelling of nitrogen at pressures up to 9 MPa II. Rotaitonal Raman linewidths,” Appl. Phys. B **75**(6-7), 771–778 (2002). [CrossRef]

_{2}) thermometry,” Opt. Lett. **34**(23), 3755–3757 (2009). [CrossRef] [PubMed]

**19**(16), 15627–15640 (2011). [CrossRef] [PubMed]

*T*is the apparent temperature with the collision-free assumption (K),

_{App}*τ*is the probe delay (ps),

_{23}*T*is the reference temperature (K), P is the pressure (atm), and

_{o}*a*are fit parameters. The coefficients have been determined with a fair degree of consistency from 1 to 20 atm and at room temperature for N

_{i}_{2}(

*a*= 7.36 × 10

_{1}^{−3}atm

^{−1},

*a*= 4.257 × 10

_{2}^{−5}atm

^{−2}ps

^{−1}, and

*a*= 1.016 × 10

_{3}^{−3}atm

^{−1}ps

^{−1}) and for O

_{2}(

*a*= 1.405 × 10

_{1}^{−3}atm

^{−1},

*a*= 1.563 × 10

_{2}^{−5}atm

^{−2}ps

^{−1}, and

*a*= 4.77 × 10

_{3}^{−4}atm

^{−1}ps

^{−1}). The reduced sensitivity of O

_{2}to collisional effects at elevated pressure is quantified by the lower values of

*a*and

_{2}*a*in the exponential term in Eq. (2). This is due to greater uniformity in linewidth across the rotational energy levels of O

_{3}_{2.}This simple model can also be used to estimate the probe delay,

*τ*, and the associated minimum probe pulse width necessary for avoiding the effects of collisions at even higher pressures with frequency-domain ps or fs/ps CARS thermometry. At 20 atm, for example, the temperature shift is as high as 14.5 K/ps for N

_{23}_{2}and 5.7 K/ps for O

_{2}. Without this knowledge, the use of longer probe delays or slight jitter between the preparation and probe pulses can cause significant variations in the apparent temperature (as high as 5% per ps).

## 4. Conclusions

_{2}and O

_{2}up to 20 atm. Utilizing fs pump and Stokes pulses and a probe-pulse delay of 6.5 ps, it is possible to avoid the effects of collisions for pressures up to 15 atm and minimize corrections for collisional effects at even higher pressures. This can be achieved while avoiding nonresonant background and isolating individual rotational transitions for accurate frequency-domain thermometry. Future work will focus on testing the interference-free assumption at higher temperatures and pressures.

## Acknowledgments

## References and links

1. | S. Roy, J. R. Gord, and A. K. Patnaik, “Recent advances in coherent anti-Stokes Raman scattering spectroscopy: Fundamental developments and applications in reacting flows,” Prog. Energ. Combust. Sci. |

2. | T. Seeger, F. Beyrau, A. Brauer, and A. Leipertz, “High-pressure pure rotational CARS: comparison of temperature measurements with O |

3. | F. Vestin, M. Afzelius, and P. E. Bengtsson, “Development of rotational CARS for combustion diagnostics using a polarization approach,” Proc. Combust. Inst. |

4. | F. M. Kamga and M. G. Sceats, “Pulse-sequenced coherent anti-Stokes Raman scattering: Method for suppression of the non-resonant background,” Opt. Lett. |

5. | H. M. Frey, P. Beaud, T. Gerber, B. Mischler, P. Radi, and A. P. Tzannis, “Femtosecond nonresonant degenerate four-wave mixing at atmospheric pressure and in a free jet,” Appl. Phys. B |

6. | P. Beaud, H. M. Frey, T. Lang, and M. Motzkus, “Flame thermometry by femtosecond CARS,” Chem. Phys. Lett. |

7. | T. R. Meyer, S. Roy, and J. R. Gord, “Improving signal-to-interference ratio in rich hydrocarbon-air flames using picosecond coherent anti-Stokes Raman scattering,” Appl. Spectrosc. |

8. | T. Seeger, J. Kiefer, A. Leipertz, B. D. Patterson, C. J. Kliewer, and T. B. Settersten, “Picosecond time-resolved pure-rotational coherent anti-Stokes Raman spectroscopy for N( |

9. | G. Knopp, P. Beaud, P. Radi, M. Tulej, B. Bougie, D. Cannavo, and T. Gerber, “Pressure-dependent N |

10. | T. Lang and M. Motzkus, “Determination of line shift coefficients with femtosecond time resolved CARS,” J. Raman Spectrosc. |

11. | T. Lang, M. Motzkus, H. M. Frey, and P. Beaud, “High resolution femtosecond coherent anti-Stokes Raman scattering: Determination of rotational constants, molecular anharmonicity, collisional line shifts, and temperature,” J. Chem. Phys. |

12. | P. Beaud and G. Knopp, “Scaling rotationally inelastic collisions with an effective angular momentum parameter,” Chem. Phys. Lett. |

13. | P. Beaud, T. Gerber, P. Radi, M. Tulej, and G. Knopp, “Rotationally inelastic collisions between N |

14. | G. Knopp, P. Radi, M. Tulej, T. Gerber, and P. Beaud, “Collision induced rotational energy transfer probed by time-resolved coherent anti-Stokes Raman scattering,” J. Chem. Phys. |

15. | T. Lang and M. Motzkus, “Single-shot femtosecond coherent anti-Stokes Raman scattering thermometry,” J. Opt. Soc. Am. B |

16. | R. P. Lucht, S. Roy, T. R. Meyer, and J. R. Gord, “Femtosecond coherent anti-Stokes Raman scattering measurement of gas temperatures from frequency-spread dephasing of the Raman coherence,” Appl. Phys. Lett. |

17. | J. D. Miller, S. Roy, M. N. Slipchenko, J. R. Gord, and T. R. Meyer, “Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering,” Opt. Express |

18. | J. D. Miller, M. N. Slipchenko, T. R. Meyer, H. U. Stauffer, and J. R. Gord, “Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering for high-speed gas-phase thermometry,” Opt. Lett. |

19. | J. D. Miller, M. N. Slipchenko, and T. R. Meyer, “Probe-pulse optimization for nonresonant suppression in hybrid fs/ps coherent anti-Stokes Raman scattering at high temperature,” Opt. Express |

20. | J. D. Miller, S. Roy, J. R. Gord, and T. R. Meyer, “Communication: Time-domain measurement of high-pressure N |

21. | B. D. Prince, A. Chakraborty, B. M. Prince, and H. U. Stauffer, “Development of simultaneous frequency- and time-resolved coherent anti-Stokes Raman scattering for ultrafast detection of molecular Raman spectra,” J. Chem. Phys. |

22. | L. A. Rahn and R. E. Palmer, “Studies of nitrogen self-broadening at high-temperature with inverse Raman-spectroscopy,” J. Opt. Soc. Am. B |

23. | B. Lavorel, H. Tran, E. Hertz, O. Faucher, P. Joubert, M. Motzkus, T. Buckup, T. Lang, H. Skenderovi, G. Knopp, P. Beaud, and H. M. Frey, “Femtosecond Raman time-resolved molecular spectroscopy,” C. R. Phys. |

24. | L. Martinsson, P. E. Bengtsson, M. Alden, S. Kroll, and J. Bonamy, “A test of different rotational Raman linewidth models: accuracy of rotational coherent anti-Stokes-Raman scattering thermometry in nitrogen from 295 to 1850 K,” J. Chem. Phys. |

25. | M. Afzelius, P. E. Bengtsson, J. Bood, J. Bonamy, F. Chaussard, H. Berger, and T. Dreier, “Dual-broadband rotational CARS modelling of nitrogen at pressures up to 9 MPa II. Rotaitonal Raman linewidths,” Appl. Phys. B |

**OCIS Codes**

(280.1740) Remote sensing and sensors : Combustion diagnostics

(300.6230) Spectroscopy : Spectroscopy, coherent anti-Stokes Raman scattering

(300.6530) Spectroscopy : Spectroscopy, ultrafast

(320.2250) Ultrafast optics : Femtosecond phenomena

(320.5390) Ultrafast optics : Picosecond phenomena

**ToC Category:**

Sensors

**History**

Original Manuscript: November 7, 2011

Revised Manuscript: December 20, 2011

Manuscript Accepted: December 23, 2011

Published: February 13, 2012

**Citation**

Joseph D. Miller, Chloe E. Dedic, Sukesh Roy, James R. Gord, and Terrence R. Meyer, "Interference-free gas-phase thermometry at elevated pressure using hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering," Opt. Express **20**, 5003-5010 (2012)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-5-5003

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### References

- S. Roy, J. R. Gord, and A. K. Patnaik, “Recent advances in coherent anti-Stokes Raman scattering spectroscopy: Fundamental developments and applications in reacting flows,” Prog. Energ. Combust. Sci.36(2), 280–306 (2010). [CrossRef]
- T. Seeger, F. Beyrau, A. Brauer, and A. Leipertz, “High-pressure pure rotational CARS: comparison of temperature measurements with O2, N2 and synthetic air,” J. Raman Spectrosc.34, 932–939 (2003). [CrossRef]
- F. Vestin, M. Afzelius, and P. E. Bengtsson, “Development of rotational CARS for combustion diagnostics using a polarization approach,” Proc. Combust. Inst.31(1), 833–840 (2007). [CrossRef]
- F. M. Kamga and M. G. Sceats, “Pulse-sequenced coherent anti-Stokes Raman scattering: Method for suppression of the non-resonant background,” Opt. Lett.5(3), 126–128 (1980). [CrossRef] [PubMed]
- H. M. Frey, P. Beaud, T. Gerber, B. Mischler, P. Radi, and A. P. Tzannis, “Femtosecond nonresonant degenerate four-wave mixing at atmospheric pressure and in a free jet,” Appl. Phys. B68(4), 735–739 (1999). [CrossRef]
- P. Beaud, H. M. Frey, T. Lang, and M. Motzkus, “Flame thermometry by femtosecond CARS,” Chem. Phys. Lett.344(3-4), 407–412 (2001). [CrossRef]
- T. R. Meyer, S. Roy, and J. R. Gord, “Improving signal-to-interference ratio in rich hydrocarbon-air flames using picosecond coherent anti-Stokes Raman scattering,” Appl. Spectrosc.61(11), 1135–1140 (2007). [CrossRef] [PubMed]
- T. Seeger, J. Kiefer, A. Leipertz, B. D. Patterson, C. J. Kliewer, and T. B. Settersten, “Picosecond time-resolved pure-rotational coherent anti-Stokes Raman spectroscopy for N(2) thermometry,” Opt. Lett.34(23), 3755–3757 (2009). [CrossRef] [PubMed]
- G. Knopp, P. Beaud, P. Radi, M. Tulej, B. Bougie, D. Cannavo, and T. Gerber, “Pressure-dependent N2 Q-branch fs-CARS measurements,” J. Raman Spectrosc.33(11-12), 861–865 (2002). [CrossRef]
- T. Lang and M. Motzkus, “Determination of line shift coefficients with femtosecond time resolved CARS,” J. Raman Spectrosc.31(1-2), 65–70 (2000). [CrossRef]
- T. Lang, M. Motzkus, H. M. Frey, and P. Beaud, “High resolution femtosecond coherent anti-Stokes Raman scattering: Determination of rotational constants, molecular anharmonicity, collisional line shifts, and temperature,” J. Chem. Phys.115(12), 5418–5426 (2001). [CrossRef]
- P. Beaud and G. Knopp, “Scaling rotationally inelastic collisions with an effective angular momentum parameter,” Chem. Phys. Lett.371(1-2), 194–201 (2003). [CrossRef]
- P. Beaud, T. Gerber, P. Radi, M. Tulej, and G. Knopp, “Rotationally inelastic collisions between N2 and rare gases: An extension of the angular momentum scaling law,” Chem. Phys. Lett.373(3-4), 251–257 (2003). [CrossRef]
- G. Knopp, P. Radi, M. Tulej, T. Gerber, and P. Beaud, “Collision induced rotational energy transfer probed by time-resolved coherent anti-Stokes Raman scattering,” J. Chem. Phys.118(18), 8223–8233 (2003). [CrossRef]
- T. Lang and M. Motzkus, “Single-shot femtosecond coherent anti-Stokes Raman scattering thermometry,” J. Opt. Soc. Am. B19(2), 340–344 (2002). [CrossRef]
- R. P. Lucht, S. Roy, T. R. Meyer, and J. R. Gord, “Femtosecond coherent anti-Stokes Raman scattering measurement of gas temperatures from frequency-spread dephasing of the Raman coherence,” Appl. Phys. Lett.89(25), 251112 (2006). [CrossRef]
- J. D. Miller, S. Roy, M. N. Slipchenko, J. R. Gord, and T. R. Meyer, “Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering,” Opt. Express19(16), 15627–15640 (2011). [CrossRef] [PubMed]
- J. D. Miller, M. N. Slipchenko, T. R. Meyer, H. U. Stauffer, and J. R. Gord, “Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering for high-speed gas-phase thermometry,” Opt. Lett.35(14), 2430–2432 (2010). [CrossRef] [PubMed]
- J. D. Miller, M. N. Slipchenko, and T. R. Meyer, “Probe-pulse optimization for nonresonant suppression in hybrid fs/ps coherent anti-Stokes Raman scattering at high temperature,” Opt. Express19(14), 13326–13333 (2011). [CrossRef] [PubMed]
- J. D. Miller, S. Roy, J. R. Gord, and T. R. Meyer, “Communication: Time-domain measurement of high-pressure N2 and O2 self-broadened linewidths using hybrid femtosecond∕picosecond coherent anti-Stokes Raman scattering,” J. Chem. Phys.135(20), 201104 (2011). [CrossRef] [PubMed]
- B. D. Prince, A. Chakraborty, B. M. Prince, and H. U. Stauffer, “Development of simultaneous frequency- and time-resolved coherent anti-Stokes Raman scattering for ultrafast detection of molecular Raman spectra,” J. Chem. Phys.125(4), 044502 (2006). [CrossRef] [PubMed]
- L. A. Rahn and R. E. Palmer, “Studies of nitrogen self-broadening at high-temperature with inverse Raman-spectroscopy,” J. Opt. Soc. Am. B3(9), 1164–1169 (1986). [CrossRef]
- B. Lavorel, H. Tran, E. Hertz, O. Faucher, P. Joubert, M. Motzkus, T. Buckup, T. Lang, H. Skenderovi, G. Knopp, P. Beaud, and H. M. Frey, “Femtosecond Raman time-resolved molecular spectroscopy,” C. R. Phys.5, 215–229 (2004). [CrossRef]
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