Femtosecond coherent anti-Stokes Raman scattering (CARS) suffers from poor selectivity between neighbouring Raman levels due to the large bandwidth of the femtosecond pulses. This paper provides a new method to real...Femtosecond coherent anti-Stokes Raman scattering (CARS) suffers from poor selectivity between neighbouring Raman levels due to the large bandwidth of the femtosecond pulses. This paper provides a new method to realize the selective excitation and suppression of femtosecond CARS by manipulating both the probe and pump (or Stokes) spectra. These theoretical results indicate that the CARS signals between neighbouring Raman levels are differentiated from their indistinguishable femtosecond CARS spectra by tailoring the probe spectrum, and then their selective excitation and suppression can be realized by supplementally manipulating the pump (or Stokes) spectrum with the π spectral phase step.展开更多
The energy dissipation mechanism of energetic materials(EMs) is very important for keeping safety. We choose nitrobenzene as a model of EM and employ transient absorption(TA) spectroscopy and time-resolved coheren...The energy dissipation mechanism of energetic materials(EMs) is very important for keeping safety. We choose nitrobenzene as a model of EM and employ transient absorption(TA) spectroscopy and time-resolved coherent anti-stokes Raman scattering(CARS) to clarify its energy dissipation mechanism. The TA data confirms that the excited nitrobenzene spends about 16 ps finishing the twist intramolecular charge transfer from benzene to nitro group, and dissipates its energy through the rapid vibration relaxation in the initial excited state. And then the dynamics of vibrational modes(VMs) in the ground state of nitrobenzene, which are located at 682 cm^-1(v1), 854 cm^-1(v2), 1006 cm^-1(v3), and 1023 cm^-1(v4),is scanned by CARS. It exhibits that the excess energy of nitrobenzene on the ground state would further dissipate through intramolecular vibrational redistribution based on the vibrational cooling of vi and v2 modes, v1 and v4 modes, and v3 and v4 modes. Moreover, the vibration-vibration coupling depends not only on the energy levels of VMs, but also on the spatial position of chemical bonds relative to the VM.展开更多
The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane(NM)molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy(CARS) tec...The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane(NM)molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy(CARS) technique with the intense pump laser. Here, we present the mechanism of molecular alignment and deformation. The CARS spectra and its FFT spectra of liquid NM show that the NO2 torsional mode couples with the CN symmetric stretching mode and that the NO2 group undergoes ultrafast structural deformation with a relaxation time of 195 fs. The frequency of the NO2 torsional mode in liquid NM(50.8±0.3 cm^-1) at room temperature is found. Our results prove the structural deformation of two groups in liquid NM molecule occur simultaneously in the intense laser field.展开更多
Coherent anti-Stokes Raman scattering spectroscopy(CARS) is a well-known detecting tool in biosensing and nonlinear spectroscopy. It can provide a non-invasive alternative without the need for exogenous labels,while...Coherent anti-Stokes Raman scattering spectroscopy(CARS) is a well-known detecting tool in biosensing and nonlinear spectroscopy. It can provide a non-invasive alternative without the need for exogenous labels,while the enhancement factor for surface plasmon resonances(SPR) are extensively used to increase the local field close to the oscillators and which can obtain high enhancement. In this work, we investigate the enhancement factor of our structure for surface-enhanced coherent anti-Stokes Raman scattering. The absorption spectrum of the structure has been studied, a wide range of absorption has been realized. The enhancement can be as high as 10^(16) over standard CARS. Our design is very useful for improving the enhancement factor of surface-enhanced coherent anti-Stokes Raman scattering.展开更多
基金Project supported by Programme for Changjiang Scholars and Innovative Research Team in University(PCSIRT)Shanghai Leading Academic Discipline Project(Grant No.B408)+3 种基金National Key Project for Basic Research of China(Grant Nos.2006CB806006 and 2006CB921105)Ministry of Education of China(Grant No.30800)Shanghai Municipal Natural Science Foundation(Grant No.09ZR1409300)Shanghai Municipal Science and Technology Commission(Grant No.07DZ22025)
文摘Femtosecond coherent anti-Stokes Raman scattering (CARS) suffers from poor selectivity between neighbouring Raman levels due to the large bandwidth of the femtosecond pulses. This paper provides a new method to realize the selective excitation and suppression of femtosecond CARS by manipulating both the probe and pump (or Stokes) spectra. These theoretical results indicate that the CARS signals between neighbouring Raman levels are differentiated from their indistinguishable femtosecond CARS spectra by tailoring the probe spectrum, and then their selective excitation and suppression can be realized by supplementally manipulating the pump (or Stokes) spectrum with the π spectral phase step.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21573094,11274142,11474131,11574112,and 51502109)the National Found for Fostering Talents of Basic Science,China(Grant No.J1103202)+1 种基金the Science Challenging Program(Grant No.JCKY2016212A501)China Scholarship Council(CSC) during a visit of Ning Sui(Grant No.201706175038) to MPIA is also acknowledged
文摘The energy dissipation mechanism of energetic materials(EMs) is very important for keeping safety. We choose nitrobenzene as a model of EM and employ transient absorption(TA) spectroscopy and time-resolved coherent anti-stokes Raman scattering(CARS) to clarify its energy dissipation mechanism. The TA data confirms that the excited nitrobenzene spends about 16 ps finishing the twist intramolecular charge transfer from benzene to nitro group, and dissipates its energy through the rapid vibration relaxation in the initial excited state. And then the dynamics of vibrational modes(VMs) in the ground state of nitrobenzene, which are located at 682 cm^-1(v1), 854 cm^-1(v2), 1006 cm^-1(v3), and 1023 cm^-1(v4),is scanned by CARS. It exhibits that the excess energy of nitrobenzene on the ground state would further dissipate through intramolecular vibrational redistribution based on the vibrational cooling of vi and v2 modes, v1 and v4 modes, and v3 and v4 modes. Moreover, the vibration-vibration coupling depends not only on the energy levels of VMs, but also on the spatial position of chemical bonds relative to the VM.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21673211 and 21203047)the Foundation of Heilongjiang Bayi Agricultural University,China(Grant No.XZR2014-16)the Science Challenging Program of China(Grant No.JCKY2016212A501)
文摘The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane(NM)molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy(CARS) technique with the intense pump laser. Here, we present the mechanism of molecular alignment and deformation. The CARS spectra and its FFT spectra of liquid NM show that the NO2 torsional mode couples with the CN symmetric stretching mode and that the NO2 group undergoes ultrafast structural deformation with a relaxation time of 195 fs. The frequency of the NO2 torsional mode in liquid NM(50.8±0.3 cm^-1) at room temperature is found. Our results prove the structural deformation of two groups in liquid NM molecule occur simultaneously in the intense laser field.
基金Project supported by the National Key Research Program of China(No.2011ZX01015-001)the National Basic Research Program of China(Nos.2011CBA00608,2012CB619203,2015CB351902,2015CB932402)
文摘Coherent anti-Stokes Raman scattering spectroscopy(CARS) is a well-known detecting tool in biosensing and nonlinear spectroscopy. It can provide a non-invasive alternative without the need for exogenous labels,while the enhancement factor for surface plasmon resonances(SPR) are extensively used to increase the local field close to the oscillators and which can obtain high enhancement. In this work, we investigate the enhancement factor of our structure for surface-enhanced coherent anti-Stokes Raman scattering. The absorption spectrum of the structure has been studied, a wide range of absorption has been realized. The enhancement can be as high as 10^(16) over standard CARS. Our design is very useful for improving the enhancement factor of surface-enhanced coherent anti-Stokes Raman scattering.