Two-photon excitation spectroscopy of 1,5–diphenyl-1,3,5-hexatriene using phase modulation

Pushpendra Kumar, Khadga Jung Karki

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


We have used two-photon Fourier transform spectroscopy to investigate the first singlet excited state (S1) of a prototypical polyene molecule 1,5—Diphenyl-1,3,5-hexatriene. As the S1 state in the polyenes is a one-photon forbidden transition, the structure of its vibrational levels cannot be studied using resonant linear excitation. Although this level is accessible with two-photon excitation, previous studies done by using wavelength tunable pulsed lasers did not have enough resolution to investigate the details of the vibrational levels. In Fourier transform spectroscopy, one uses a pair of laser beams to excite the sample. The measurements are done by varying the time delay between the pulses. The spectral resolution is given by the inverse of the maximum time delay rather than the spectral width of the pulses. We have used the method to investigate the vibrational levels of the S1 state. In our implementation, we have used phase modulation to carry out the measurements in the rotating frame, which requires less data points along the time delay thereby significantly reducing the measurement time.

Original languageEnglish
Article number035008
JournalJournal of Physics Communications
Issue number3
StatePublished - Mar 2019
Externally publishedYes


  • Excited states of diphenyl hexa-triene
  • Fourier transform spectroscopy
  • Two-photon excitation


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