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Watching the coherence of multiple vibrational states in organic dye molecules by using supercontinuum probing photon echo spectroscopy
Chemical Physics Letters 517 (2011) 242–245
Contents lists available at SciVerse ScienceDirect
Chemical Physics Letters journal homepage: www.elsevier.com/locate/cplett
Watching the coherence of multiple vibrational states in organic dye molecules by using supercontinuum probing photon echo spectroscopy Guoyang Yu, Yunfei Song, Yang Wang, Xing He, Yuqiang Liu, Weilong Liu, Yanqiang Yang ⇑ Center for Condensed Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150001, China
a r t i c l e
i n f o
Article history: Received 27 December 2010 In final form 21 October 2011 Available online 28 October 2011
a b s t r a c t A modified photon echo (PE) technique, the supercontinuum probing photon echo (SCPPE), is introduced and performed to investigate the vibrational coherence in organic dye IR780 perchlorate doped polyvinyl alcohol (PVA) film. The coherences of multiple vibrational states which belong to four vibrational modes create complex oscillations in SCPPE signal. The frequencies of vibrational modes are confirmed from the results of Raman calculation which accord fairly well with the results of Raman scattering experiment. Compared with conventional one-color PE, the SCPPE technique can realize broadband detection and make the experiment about vibrational coherence more efficient. Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction Vibrational coherence is a common phenomenon in optical transition and plays an important role in some physical processes. In electron transfer, the charge-separation is influenced significantly by vibrational coherence [1,2]. Moreover in quantum computation, a stable system which can be coherently manipulated and controlled is expected eagerly because this is an important step towards implementation of a quantum computer [3,4]. All of these applications need the information concerning vibrational coherence. When vibrational states are excited coherently, the intensity of signal is modulated periodically and oscillations are observed in time domain. Thus, the vibrational coherence can be investigated by analyzing the oscillations in time-resolved spectroscopy. With the development of ultrafast laser, PE spectroscopy proves to be a powerful method to investigate vibrational coherence [5– 8]. The PE spectroscopy can be divided into one- or two-color PE according to whether the wavelengths of excitation and probe pulses are the same. One-color PE spectroscopy is only sensitive to the information within the spectral range of the excitation pulse [9,10]. However, for complex molecules, the population in fourwave mixing (FWM) usually oversteps the spectral range of the excitation pulse. So wavelength of probe pulse is changed to achieve a broader detection range [11–13] and this method is two-color PE. However, in order to change the wavelength of probe pulse, optical parameter amplifier (OPA) are usually used in two-color PE, which makes the whole experimental setup more complex and sets a high request to output power of light source. Moreover, two-color PE is still a narrow-band detection method ⇑ Corresponding author. E-mail address: [email protected] (Y. Yang). 0009-2614/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cplett.2011.10.049
for a single scan. Thus, two-color PE can only detect the vibrational coherence among the vibrational states whose energy difference is within the bandwidth of probe pulse. To overcome these difficulties, we propose to use supercontinuum (SC) as probe pulse instead of general femtosecond laser pulse. In this approach, the input power producing SC is much lower than that of OPA, which makes the experiment more flexible and simpler. And most importantly, the bandwidth of SC can realize a broadband detection, which ensures that the vibrational coherences among all stimulated vibrational states can be observed. In this work, organic dye IR780 perchlorate doped PVA film is used to validate the feasibility and reasonability of SCPPE. The result shows that the coherences of multiple vibrational states and demonstrates that the SCPPE can indeed realize the broadband detection compared with one-color PE results. 2. Experiment The SCPPE setup is shown in Figure 1a. The ultrafast pulse (100 fs, 800 nm, 1 kHz) generated by a Ti:sapphire regeneration amplified laser system (Spectra-Physics, Spitfire) is split into three. Two of them with wave vector k1 and k2 act as excitation pulses. The third one is focused with an f = 50 mm lens onto the sapphire crystal to generate SC with wave vector k3 and collimated with a telescope system. The three beams have the same polarization and are focused and spatially cross at one point on the IR780 perchlorate/PVA film using folded box geometry. The pulses overlapping in time domain are adjusted by optical delay line. The interval between the two excitation pulses (t12) is fixed on 50 fs to achieve rephasing, and the interval between the second excitation and probe pulses (t23) is scanned. The PE signal along phase-matching direction k4 = k1 + k2 + k3 is captured by a spectrometer (Optics 250IS/SM, Bruker) equipped with an intensified
G. Yu et al. / Chemical Physics Letters 517 (2011) 242–245
243
Figure 1. (a) Schematic of experimental setup. BS: beam splitter, PS: periscope. (b) Energy level diagrams describing optical transition in PE technique. The left and right diagrams describe pathways that propagate on the excited and ground states, respectively. The solid and dashed vertical arrows refer to excitations on the ket and bra side of density matrix, respectively. And the horizontal lines denoted by jiji (i, j = 0, 1, 2) refer to vibrational states on the electronic ground and excited states. The Gaussian curves indicate the bandwidth of excitation and probe pulses.
charge-coupled device (Andor iStar, DH720). The organic dye IR780 perchlorate doped PVA film is prepared by spin coating and air drying at room temperature. The SCPPE technique is appropriate to study vibrational coherence due to its broadband detection characteristic. As shown in Figure 1b, the molecule is stimulated from electronic ground state to excited state. The population distribution usually oversteps the bandwidth of excitation pulse due to the effect of nonradiative transition such as vibrational cooling (VC) and vibrational energy transfer (VET). In one-color PE technique, the probe pulse is the same as the excitation pulse, so the one-color PE cannot detect the vibrational coherence between the vibrational states exceeding the bandwidth of excitation pulse such as vibrational states j10ie and j20ie as shown in Figure 1b. To achieve broader detection range in frequency domain, the wavelength of probe pulse is changed and this PE technique is named two-color PE. In two-color PE technique, the sample will be scanned time after time when the wavelength of probe pulse is changed. In fact, two-color PE is still narrow-band detection for every single scan; it cannot detect vibrational coherence between the vibrational states exceeding the bandwidth of probe pulse such as vibrational states j00ie and j20ie as shown in Figure 1b. The SCPPE can solve this problem existing in the conventional PE techniques. In SCPPE technique, the bandwidth of SC ensures to achieve the same detection region as two-color PE. And the SCPPE is a truly broadband detection spectroscopy which allows to detect the vibrational coherence among all vibrational states stimulated in a single scan. The information concerning SC in near infrared (NIR) region is obtained by optical Kerr gate. As shown in Figure 2, the SC has dispersion in NIR region and the influence for the PE signal can be eliminated by dispersion correction. In addition, the pulsewidth (tw) of SC is widened due to the dispersion. However, the temporal duration (td) at a certain wavelength, such as 796 nm, 800 nm, 804 nm and 809 nm, is only widened a little and almost the same as that of the femtosecond laser pulse which is used to generate SC. Therefore, the widening of pulsewidth of SC almost has no effect on temporal resolution in SCPPE.
3. Results and discussion The excitation pulse wavelength lies in the absorption band of molecular system as shown in Figure 3a, which indicates that the molecular system is stimulated resonantly from electronic ground
Figure 2. The dispersion curve of SC in NIR region. The tw denotes the pulsewidth of SC in NIR region. The inset shows the temporal duration (td) at 796 nm, 800 nm, 804 nm and 809 nm.
state to excited state. Here, the SCPPE is compared with one-color PE. In one-color PE, the probe pulse is the same as excitation pulse. Obviously, detection range of SCPPE is much broader than that of one-color PE through comparison between the spectra of SC and excitation pulse. And the bandwidth of SCPPE signal is also broader than that of one-color PE, which indicates that more vibrational states can be probed in SCPPE signal. In addition, the SCPPE and one-color PE signals have the red shift and blue shift respectively, which indicates that the two signals results from coupling strengths of different vibrational modes. The vibrational coherence can be observed as oscillations in time domain. As shown in Figure 3b, the oscillations are diverse at different wavelengths. After subtracting exponential decay components, the oscillations at different wavelengths are shown in Figure 4a. These oscillations can be attributed to coherence of multiple vibrational states on excited state [14]. The frequency components concerning vibrational coherence can be obtained from Fourier transform of oscillations. And vibrational modes related to vibrational coherence are usually confirmed by Raman spectrum according to Franck–Condon principle [6]. Here, Gaussian 03 is performed to confirm wavenumbers of vibrational modes [15]. The Raman frequency calculation is carried out by density functional theory (DFT) with correlation
244
G. Yu et al. / Chemical Physics Letters 517 (2011) 242–245
Figure 3. (a) The SCPPE signal (solid line), SC (dash line), excitation pulse (dash dot line), one-color PE signal (dash dot line) and absorption spectra (short dash line). (b) The contour plot of SCPPE signal spectrum.
Figure 4. (a) Oscillations in SCPPE signal at 796 nm, 800 nm, 804 nm, and 809 nm. (b) Fourier transforms for SCPPE signal at corresponding wavelengths. (c) Oscillations in one-color PE signal at 797 nm. (d) Fourier transforms for one-color PE signal at 797 nm.
functional B3LYP and the basis set is 6-31G (d, p). It can be seen that the calculated wavenumbers accord fairly well with the experimental ones (Table 1), which indicates the results of calculation are reliable. According to results of Raman calculation, the frequency components of vibrational coherence are denoted in Figure 4b. The Table 1 The low-frequency vibrational modes. Vibrational mode
v1 v2 v3 v4 v5 v6 v7 v8 v9 v10
Wavenumber Calculation (cm1)
Experiment (cm1)
110 190 350 410 532 580 600 670 740 920
... ... 340 432 540 582 603 669 736 945
vibrational mode with 187 cm1 which roots in N–CH3 bond rotation (denoted v2 in Table 1) is observed at all four wavelengths. And the vibrational modes with 125 cm1 and 359 cm1 which are respectively assigned to the in-plane and out-of-plane distortions (denoted v1 and v3) are observed at two wavelengths, 796 nm and 800 nm, even though their strengths are weak. And the vibrational mode with 421 cm1 corresponding to C–C@C bond degenerate bending in conjugated branch (denoted v4) appears at two wavelengths, 800 nm and 804 nm. In addition, the second harmonic of vibrational mode v1 and v2 with 250 cm1 and 375 cm1 are obtained at wavelength 800 nm. Meanwhile, some other peaks corresponding to combinations of the fundamental frequencies (e.g. v2v1 peak at 62 cm1, v3v1 peak at 234 cm1, and v32v1 peak at 109 cm1) can also be observed in Figure 4b. These results show that the vibrational modes, such as N–CH3 bond rotation, in-plane and out-plane distortion, are coupled through vibrational coherence. In contrast, the oscillation in one-color PE signal is observed at 797 nm as shown in Figure 4c, which indicates that the vibrational coherence also exists in this signal. However, only the difference frequency of two vibrational modes (v3v2 at 156 cm1) is obtained from Fourier transform of oscillations as
G. Yu et al. / Chemical Physics Letters 517 (2011) 242–245
shown in Figure 4d, which indicates that bandwidth of probe pulse only covers two vibrational states. Therefore, compared with onecolor PE, the SCPPE has a broadband detection which ensures it is able to watch the coherence of multiple vibrational states.
4. Conclusion These experimental results show that the SCPPE technique is an effective method to detect vibrational coherence among multiple vibrational states. Compared with conventional PE, this approach can realize the broadband detection with a single scan, which can make the investigation concerning vibrational coherence more effective and simpler. And this approach will be widely performed to investigate intramolecular vibrations in the future. Acknowledgements This work was partly supported by Defense Industrial Technology Development Program of China, No. B1520110002, and it was also supported by The Pre-Research foundation of CPLA General Armament Department, No. 9104C6709101106. The experiments
245
were financially supported by National Science Foundation of China, Nos. 20973050 and 21173063. References [1] M.H. Vos, J. Lambry, S.J. Robles, D.C. Youvan, J. Breton, J. Martin, Proc. Natl. Acad. Sci. 88 (1991) 8885. [2] K.L. Dillman, W.F. Beck, J. Phys. Chem. B 114 (2010) 15269. [3] Ch. Roos et al., Phys. Rev. Letts. 83 (1999) 4713. [4] Mattguhs P.A. Brabdergirst, P. Londero, P. Wasylczuk, C. Brif, R.L. Kosut, H. Rabitz, I.A. Walmsley, Sci 320 (2008) 638. [5] D.S. Larsen, K. Ohta, Q.H. Xu, M. Cyrier, G.R. Fleming, J. Chem. Phys. 114 (2001) 8008. [6] K. Ohta, D.S. Larsen, M. Yang, G.R. Fleming, J. Chem. Phys. 114 (2001) 8020. [7] I. Pastirk, V.V. Lozovoy, M. Dantus, Chem. Phys. Letts. 333 (2001) 76. [8] L.D. Book, N.F. Scherer, J. Chem. Phys. 111 (1999) 792. [9] V.S. Lobkov, A.V. Leontiev, K.M. Salikhov, V.V. Samartsev, G.M. Safiullin, V.A. Zuikov, Laser Phys. Lett. 3 (2006) 485. [10] V.S. Lobkov, K.M. Salikhov, V.V. Samartsev, G.M. Safiullin, V.A. Zuikov, Laser Phys. Lett. 1 (2006) 26. [11] L.V. Dao, M. Lowe, P. Hannaford, Appl. Phys. Lett. 81 (2002) 1806. [12] L.V. Dao, C. Lincoln, M. Lowe, P. Hannaford, Physica B 327 (2003) 123. [13] L.V. Dao, C. Lincoln, M. Lowe, P. Hannaford, J. Chem. Phys. 120 (2004) 8434. [14] H. Abramczyk, Introduction to Laser Spectroscopy, Elsevier, Amsterdam, 2005, pp. 212–214. [15] M.J. Frisch et al., Gaussian 03, Revision E.01, Gaussian, Inc., Wallingford CT, 2004.
Contents lists available at SciVerse ScienceDirect
Chemical Physics Letters journal homepage: www.elsevier.com/locate/cplett
Watching the coherence of multiple vibrational states in organic dye molecules by using supercontinuum probing photon echo spectroscopy Guoyang Yu, Yunfei Song, Yang Wang, Xing He, Yuqiang Liu, Weilong Liu, Yanqiang Yang ⇑ Center for Condensed Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150001, China
a r t i c l e
i n f o
Article history: Received 27 December 2010 In final form 21 October 2011 Available online 28 October 2011
a b s t r a c t A modified photon echo (PE) technique, the supercontinuum probing photon echo (SCPPE), is introduced and performed to investigate the vibrational coherence in organic dye IR780 perchlorate doped polyvinyl alcohol (PVA) film. The coherences of multiple vibrational states which belong to four vibrational modes create complex oscillations in SCPPE signal. The frequencies of vibrational modes are confirmed from the results of Raman calculation which accord fairly well with the results of Raman scattering experiment. Compared with conventional one-color PE, the SCPPE technique can realize broadband detection and make the experiment about vibrational coherence more efficient. Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction Vibrational coherence is a common phenomenon in optical transition and plays an important role in some physical processes. In electron transfer, the charge-separation is influenced significantly by vibrational coherence [1,2]. Moreover in quantum computation, a stable system which can be coherently manipulated and controlled is expected eagerly because this is an important step towards implementation of a quantum computer [3,4]. All of these applications need the information concerning vibrational coherence. When vibrational states are excited coherently, the intensity of signal is modulated periodically and oscillations are observed in time domain. Thus, the vibrational coherence can be investigated by analyzing the oscillations in time-resolved spectroscopy. With the development of ultrafast laser, PE spectroscopy proves to be a powerful method to investigate vibrational coherence [5– 8]. The PE spectroscopy can be divided into one- or two-color PE according to whether the wavelengths of excitation and probe pulses are the same. One-color PE spectroscopy is only sensitive to the information within the spectral range of the excitation pulse [9,10]. However, for complex molecules, the population in fourwave mixing (FWM) usually oversteps the spectral range of the excitation pulse. So wavelength of probe pulse is changed to achieve a broader detection range [11–13] and this method is two-color PE. However, in order to change the wavelength of probe pulse, optical parameter amplifier (OPA) are usually used in two-color PE, which makes the whole experimental setup more complex and sets a high request to output power of light source. Moreover, two-color PE is still a narrow-band detection method ⇑ Corresponding author. E-mail address: [email protected] (Y. Yang). 0009-2614/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cplett.2011.10.049
for a single scan. Thus, two-color PE can only detect the vibrational coherence among the vibrational states whose energy difference is within the bandwidth of probe pulse. To overcome these difficulties, we propose to use supercontinuum (SC) as probe pulse instead of general femtosecond laser pulse. In this approach, the input power producing SC is much lower than that of OPA, which makes the experiment more flexible and simpler. And most importantly, the bandwidth of SC can realize a broadband detection, which ensures that the vibrational coherences among all stimulated vibrational states can be observed. In this work, organic dye IR780 perchlorate doped PVA film is used to validate the feasibility and reasonability of SCPPE. The result shows that the coherences of multiple vibrational states and demonstrates that the SCPPE can indeed realize the broadband detection compared with one-color PE results. 2. Experiment The SCPPE setup is shown in Figure 1a. The ultrafast pulse (100 fs, 800 nm, 1 kHz) generated by a Ti:sapphire regeneration amplified laser system (Spectra-Physics, Spitfire) is split into three. Two of them with wave vector k1 and k2 act as excitation pulses. The third one is focused with an f = 50 mm lens onto the sapphire crystal to generate SC with wave vector k3 and collimated with a telescope system. The three beams have the same polarization and are focused and spatially cross at one point on the IR780 perchlorate/PVA film using folded box geometry. The pulses overlapping in time domain are adjusted by optical delay line. The interval between the two excitation pulses (t12) is fixed on 50 fs to achieve rephasing, and the interval between the second excitation and probe pulses (t23) is scanned. The PE signal along phase-matching direction k4 = k1 + k2 + k3 is captured by a spectrometer (Optics 250IS/SM, Bruker) equipped with an intensified
G. Yu et al. / Chemical Physics Letters 517 (2011) 242–245
243
Figure 1. (a) Schematic of experimental setup. BS: beam splitter, PS: periscope. (b) Energy level diagrams describing optical transition in PE technique. The left and right diagrams describe pathways that propagate on the excited and ground states, respectively. The solid and dashed vertical arrows refer to excitations on the ket and bra side of density matrix, respectively. And the horizontal lines denoted by jiji (i, j = 0, 1, 2) refer to vibrational states on the electronic ground and excited states. The Gaussian curves indicate the bandwidth of excitation and probe pulses.
charge-coupled device (Andor iStar, DH720). The organic dye IR780 perchlorate doped PVA film is prepared by spin coating and air drying at room temperature. The SCPPE technique is appropriate to study vibrational coherence due to its broadband detection characteristic. As shown in Figure 1b, the molecule is stimulated from electronic ground state to excited state. The population distribution usually oversteps the bandwidth of excitation pulse due to the effect of nonradiative transition such as vibrational cooling (VC) and vibrational energy transfer (VET). In one-color PE technique, the probe pulse is the same as the excitation pulse, so the one-color PE cannot detect the vibrational coherence between the vibrational states exceeding the bandwidth of excitation pulse such as vibrational states j10ie and j20ie as shown in Figure 1b. To achieve broader detection range in frequency domain, the wavelength of probe pulse is changed and this PE technique is named two-color PE. In two-color PE technique, the sample will be scanned time after time when the wavelength of probe pulse is changed. In fact, two-color PE is still narrow-band detection for every single scan; it cannot detect vibrational coherence between the vibrational states exceeding the bandwidth of probe pulse such as vibrational states j00ie and j20ie as shown in Figure 1b. The SCPPE can solve this problem existing in the conventional PE techniques. In SCPPE technique, the bandwidth of SC ensures to achieve the same detection region as two-color PE. And the SCPPE is a truly broadband detection spectroscopy which allows to detect the vibrational coherence among all vibrational states stimulated in a single scan. The information concerning SC in near infrared (NIR) region is obtained by optical Kerr gate. As shown in Figure 2, the SC has dispersion in NIR region and the influence for the PE signal can be eliminated by dispersion correction. In addition, the pulsewidth (tw) of SC is widened due to the dispersion. However, the temporal duration (td) at a certain wavelength, such as 796 nm, 800 nm, 804 nm and 809 nm, is only widened a little and almost the same as that of the femtosecond laser pulse which is used to generate SC. Therefore, the widening of pulsewidth of SC almost has no effect on temporal resolution in SCPPE.
3. Results and discussion The excitation pulse wavelength lies in the absorption band of molecular system as shown in Figure 3a, which indicates that the molecular system is stimulated resonantly from electronic ground
Figure 2. The dispersion curve of SC in NIR region. The tw denotes the pulsewidth of SC in NIR region. The inset shows the temporal duration (td) at 796 nm, 800 nm, 804 nm and 809 nm.
state to excited state. Here, the SCPPE is compared with one-color PE. In one-color PE, the probe pulse is the same as excitation pulse. Obviously, detection range of SCPPE is much broader than that of one-color PE through comparison between the spectra of SC and excitation pulse. And the bandwidth of SCPPE signal is also broader than that of one-color PE, which indicates that more vibrational states can be probed in SCPPE signal. In addition, the SCPPE and one-color PE signals have the red shift and blue shift respectively, which indicates that the two signals results from coupling strengths of different vibrational modes. The vibrational coherence can be observed as oscillations in time domain. As shown in Figure 3b, the oscillations are diverse at different wavelengths. After subtracting exponential decay components, the oscillations at different wavelengths are shown in Figure 4a. These oscillations can be attributed to coherence of multiple vibrational states on excited state [14]. The frequency components concerning vibrational coherence can be obtained from Fourier transform of oscillations. And vibrational modes related to vibrational coherence are usually confirmed by Raman spectrum according to Franck–Condon principle [6]. Here, Gaussian 03 is performed to confirm wavenumbers of vibrational modes [15]. The Raman frequency calculation is carried out by density functional theory (DFT) with correlation
244
G. Yu et al. / Chemical Physics Letters 517 (2011) 242–245
Figure 3. (a) The SCPPE signal (solid line), SC (dash line), excitation pulse (dash dot line), one-color PE signal (dash dot line) and absorption spectra (short dash line). (b) The contour plot of SCPPE signal spectrum.
Figure 4. (a) Oscillations in SCPPE signal at 796 nm, 800 nm, 804 nm, and 809 nm. (b) Fourier transforms for SCPPE signal at corresponding wavelengths. (c) Oscillations in one-color PE signal at 797 nm. (d) Fourier transforms for one-color PE signal at 797 nm.
functional B3LYP and the basis set is 6-31G (d, p). It can be seen that the calculated wavenumbers accord fairly well with the experimental ones (Table 1), which indicates the results of calculation are reliable. According to results of Raman calculation, the frequency components of vibrational coherence are denoted in Figure 4b. The Table 1 The low-frequency vibrational modes. Vibrational mode
v1 v2 v3 v4 v5 v6 v7 v8 v9 v10
Wavenumber Calculation (cm1)
Experiment (cm1)
110 190 350 410 532 580 600 670 740 920
... ... 340 432 540 582 603 669 736 945
vibrational mode with 187 cm1 which roots in N–CH3 bond rotation (denoted v2 in Table 1) is observed at all four wavelengths. And the vibrational modes with 125 cm1 and 359 cm1 which are respectively assigned to the in-plane and out-of-plane distortions (denoted v1 and v3) are observed at two wavelengths, 796 nm and 800 nm, even though their strengths are weak. And the vibrational mode with 421 cm1 corresponding to C–C@C bond degenerate bending in conjugated branch (denoted v4) appears at two wavelengths, 800 nm and 804 nm. In addition, the second harmonic of vibrational mode v1 and v2 with 250 cm1 and 375 cm1 are obtained at wavelength 800 nm. Meanwhile, some other peaks corresponding to combinations of the fundamental frequencies (e.g. v2v1 peak at 62 cm1, v3v1 peak at 234 cm1, and v32v1 peak at 109 cm1) can also be observed in Figure 4b. These results show that the vibrational modes, such as N–CH3 bond rotation, in-plane and out-plane distortion, are coupled through vibrational coherence. In contrast, the oscillation in one-color PE signal is observed at 797 nm as shown in Figure 4c, which indicates that the vibrational coherence also exists in this signal. However, only the difference frequency of two vibrational modes (v3v2 at 156 cm1) is obtained from Fourier transform of oscillations as
G. Yu et al. / Chemical Physics Letters 517 (2011) 242–245
shown in Figure 4d, which indicates that bandwidth of probe pulse only covers two vibrational states. Therefore, compared with onecolor PE, the SCPPE has a broadband detection which ensures it is able to watch the coherence of multiple vibrational states.
4. Conclusion These experimental results show that the SCPPE technique is an effective method to detect vibrational coherence among multiple vibrational states. Compared with conventional PE, this approach can realize the broadband detection with a single scan, which can make the investigation concerning vibrational coherence more effective and simpler. And this approach will be widely performed to investigate intramolecular vibrations in the future. Acknowledgements This work was partly supported by Defense Industrial Technology Development Program of China, No. B1520110002, and it was also supported by The Pre-Research foundation of CPLA General Armament Department, No. 9104C6709101106. The experiments
245
were financially supported by National Science Foundation of China, Nos. 20973050 and 21173063. References [1] M.H. Vos, J. Lambry, S.J. Robles, D.C. Youvan, J. Breton, J. Martin, Proc. Natl. Acad. Sci. 88 (1991) 8885. [2] K.L. Dillman, W.F. Beck, J. Phys. Chem. B 114 (2010) 15269. [3] Ch. Roos et al., Phys. Rev. Letts. 83 (1999) 4713. [4] Mattguhs P.A. Brabdergirst, P. Londero, P. Wasylczuk, C. Brif, R.L. Kosut, H. Rabitz, I.A. Walmsley, Sci 320 (2008) 638. [5] D.S. Larsen, K. Ohta, Q.H. Xu, M. Cyrier, G.R. Fleming, J. Chem. Phys. 114 (2001) 8008. [6] K. Ohta, D.S. Larsen, M. Yang, G.R. Fleming, J. Chem. Phys. 114 (2001) 8020. [7] I. Pastirk, V.V. Lozovoy, M. Dantus, Chem. Phys. Letts. 333 (2001) 76. [8] L.D. Book, N.F. Scherer, J. Chem. Phys. 111 (1999) 792. [9] V.S. Lobkov, A.V. Leontiev, K.M. Salikhov, V.V. Samartsev, G.M. Safiullin, V.A. Zuikov, Laser Phys. Lett. 3 (2006) 485. [10] V.S. Lobkov, K.M. Salikhov, V.V. Samartsev, G.M. Safiullin, V.A. Zuikov, Laser Phys. Lett. 1 (2006) 26. [11] L.V. Dao, M. Lowe, P. Hannaford, Appl. Phys. Lett. 81 (2002) 1806. [12] L.V. Dao, C. Lincoln, M. Lowe, P. Hannaford, Physica B 327 (2003) 123. [13] L.V. Dao, C. Lincoln, M. Lowe, P. Hannaford, J. Chem. Phys. 120 (2004) 8434. [14] H. Abramczyk, Introduction to Laser Spectroscopy, Elsevier, Amsterdam, 2005, pp. 212–214. [15] M.J. Frisch et al., Gaussian 03, Revision E.01, Gaussian, Inc., Wallingford CT, 2004.