High-resolution spectroscopic probing of allowed and forbidden ortho- and para-nuclear spin-isomers of NH3.
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| Title: | High-resolution spectroscopic probing of allowed and forbidden ortho- and para-nuclear spin-isomers of NH |
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| Authors: | Patra, Indrayani1 (AUTHOR), Chakraborty, Soumyadipta1 (AUTHOR), Pal, Ardhendu1 (AUTHOR), Panda, Biswajit1 (AUTHOR), Pradhan, Manik1 (AUTHOR) manik.pradhan@bose.res.in |
| Source: | Journal of Chemical Sciences. Sep2024, Vol. 136 Issue 3, p1-7. 7p. |
| Subjects: | Cavity-ringdown spectroscopy, Quantum cascade lasers, Isomers, Chemical processes, Nuclear spin |
| Abstract: | Ammonia (NH3) is a pyramidal symmetric top molecule with inversion motion and it exists in two distinct nuclear spin isomeric forms, ortho-NH3 (K = 3n) and para-NH3 (K ≠ 3n). Here, a pair of electric dipole-allowed [RQ(4,3) and PP(2,2)] and weak forbidden [OP(3,3) and SQ(8,1)] transitions of gas-phase NH3 were probed in the ν4 fundamental vibrational band occurring at 6.2 µm mid-IR interference-free spectral region using an external-cavity quantum cascade laser coupled cavity ring-down spectrometer. We have experimentally achieved the ortho-to-para ratio (OPR) of (1.03 ± 0.24) and (1.08 ± 0.14) at room temperature (296 K) for the allowed and forbidden transitions of NH3, respectively. Furthermore, our experimental findings confirm that the nuclear spin-symmetry is conserved under the nonreactive perturber-induced collisional processes. This study paves the way to directly probe the nuclear spin-isomers of gas-phase NH3 and thus may lead to an in-depth understanding of nuclear spin-isomerism associated with various physical and chemical processes. This work shows the high-resolution probing of ortho- and para-nuclear spin-isomers of NH3 in the gas phase at room temperature using quantum cascade laser coupled cavity ring-down spectroscopy at 6.2 µm mid-IR spectral region. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Ammonia (NH3) is a pyramidal symmetric top molecule with inversion motion and it exists in two distinct nuclear spin isomeric forms, ortho-NH3 (K = 3n) and para-NH3 (K ≠ 3n). Here, a pair of electric dipole-allowed [RQ(4,3) and PP(2,2)] and weak forbidden [OP(3,3) and SQ(8,1)] transitions of gas-phase NH3 were probed in the ν4 fundamental vibrational band occurring at 6.2 µm mid-IR interference-free spectral region using an external-cavity quantum cascade laser coupled cavity ring-down spectrometer. We have experimentally achieved the ortho-to-para ratio (OPR) of (1.03 ± 0.24) and (1.08 ± 0.14) at room temperature (296 K) for the allowed and forbidden transitions of NH3, respectively. Furthermore, our experimental findings confirm that the nuclear spin-symmetry is conserved under the nonreactive perturber-induced collisional processes. This study paves the way to directly probe the nuclear spin-isomers of gas-phase NH3 and thus may lead to an in-depth understanding of nuclear spin-isomerism associated with various physical and chemical processes. This work shows the high-resolution probing of ortho- and para-nuclear spin-isomers of NH3 in the gas phase at room temperature using quantum cascade laser coupled cavity ring-down spectroscopy at 6.2 µm mid-IR spectral region. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 09743626 |
| DOI: | 10.1007/s12039-024-02281-7 |
