Polarization dependence of the resonant two‐photon ionization spectra of jet‐cooled (1R,2R)‐(−)‐pseudoephedrine

• Published in: Bulletin of the Korean Chemical Society 2022, 43(3), , pp.369-375
• Main Authors: Jeong, Changseop, Mishra, Kamal K., Yun, Jiyeon, Heo, Jiyoung, Kim, Nam Joon
• Format: Article
• Language: English
• Subjects: circularly polarized light; molecular alignment; polarization of light; resonant two‐photon ionization; transition probability; 화학
• ISSN: 1229-5949; 0253-2964; 1229-5949
• DOI: 10.1002/bkcs.12473

The polarization dependence of the resonant two‐photon ionization (R2PI) spectra of jet‐cooled (1R,2R)‐(−)‐pseudoephedrine was investigated near the origin bands of three conformers. To obtain the difference R2PI spectra of the origin bands, R2PI signals produced by circularly polarized light (CP) were subtracted from those produced by linearly polarized light (LP), which revealed positive values for the P and R branches of the origin bands and negative values for the Q branch. To understand the different polarization behaviors of the P, Q, and R branches, expressions were derived to predict the transition probabilities of symmetric top molecules in a parallel transition. The transition probabilities varied depending on the direction of the total angular momentum J with respect to the light propagation vector. The different polarization behaviors of the rotational branches may arise from the differences in the angular distributions of the J vectors that are preferentially excited by LP and CP. The difference resonant two‐photon ionization spectra of linearly and circularly polarized light showed positive values for the P and R branches of the electronic band origin and negative values for the Q branch.