Stephen T. Pratt , Ugo Jacovella , Séverine Boyé-Péronne , Michael N.R. Ashfold , Denis Joyeux , Nelson De Oliveira , David M.P. Holland
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This region extends from just above the Franck-Condon envelope for the <span><math><mover><mi>A</mi><mo>̃</mo></mover></math></span> <sup>1</sup><span><math><mrow><msub><mi>A</mi><mrow><mn>2</mn></mrow></msub><mo>″</mo></mrow></math></span> ← <span><math><mover><mi>X</mi><mo>̃</mo></mover></math></span> <sup>1</sup><span><math><mrow><msub><mi>A</mi><mrow><mn>1</mn></mrow></msub><mo>′</mo></mrow></math></span> transition to well above the NH<sub>3</sub><sup>+</sup> <span><math><msup><mrow><mover><mi>X</mi><mo>̃</mo></mover></mrow><mo>+</mo></msup></math></span> <sup>2</sup><span><math><mrow><msub><mi>A</mi><mrow><mn>2</mn></mrow></msub><mo>″</mo></mrow></math></span> ionization threshold. The spectra were recorded at a measured resolution of 0.23 cm<sup>−1</sup> in both a room-temperature cell (293 K) and in a slit-jet supersonic expansion (∼70 K). The absolute photoabsorption cross section with an uncertainty of ± 5% is also reported for the room-temperature spectrum. The present resolution is a factor of 10 – 100 times higher than in other recently reported broad band spectra of ammonia, and many of the observed bands show partially resolved rotational structure. We have attempted to assign this structure for a number of these bands. The oscillator strengths extracted from the data are in good agreement with previous measurements but, in the case of structured bands, the present higher resolution measurements return higher peak absorption cross sections, that increase further when the sample is cooled. The present higher resolution spectra suggest that a number of previous vibronic band assignments that were based on quantum defect considerations may require some revision. Finally, we discuss the substantial differences between the photoabsorption and photoionization data just above the first ionization threshold.</p></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4000,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"High-resolution absorption spectroscopy of room-temperature and jet-cooled ammonia between 59,000 and 93,000 cm−1\",\"authors\":\"Stephen T. Pratt , Ugo Jacovella , Séverine Boyé-Péronne , Michael N.R. Ashfold , Denis Joyeux , Nelson De Oliveira , David M.P. Holland\",\"doi\":\"10.1016/j.jms.2023.111810\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>We present new high-resolution photoabsorption spectra of ammonia spanning the region between 59,000 cm<sup>−1</sup> and 93,000 cm<sup>−1</sup> that were recorded by using the Fourier Transform Spectrometer at the Synchrotron SOLEIL. 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引用次数: 0
摘要
利用同步加速器SOLEIL的傅里叶变换光谱仪记录了氨在59,000 cm - 1和93,000 cm - 1之间的高分辨率光吸收光谱。这个区域从刚好高于frank - condon包络层的Ã 1A2″←X²1A1 '跃迁延伸到远高于NH3+ X²²²″电离阈值。在室温电池(293 K)和缝流射流超音速膨胀(~ 70 K)下,以0.23 cm−1的测量分辨率记录了光谱。室温光谱的绝对光吸收截面的不确定度为±5%。目前的分辨率比其他最近报道的氨的宽带光谱高10 - 100倍,并且许多观察到的波段显示部分分解的旋转结构。我们已经尝试将这种结构分配给许多这样的波段。从数据中提取的振荡器强度与先前的测量结果很好地一致,但是,在结构化波段的情况下,目前更高分辨率的测量结果返回更高的峰值吸收截面,当样品冷却时,这一峰值吸收截面进一步增加。目前的高分辨率光谱表明,以前一些基于量子缺陷考虑的振动带分配可能需要一些修正。最后,我们讨论了光吸收和光电离数据在第一电离阈值以上的实质性差异。
High-resolution absorption spectroscopy of room-temperature and jet-cooled ammonia between 59,000 and 93,000 cm−1
We present new high-resolution photoabsorption spectra of ammonia spanning the region between 59,000 cm−1 and 93,000 cm−1 that were recorded by using the Fourier Transform Spectrometer at the Synchrotron SOLEIL. This region extends from just above the Franck-Condon envelope for the 1 ← 1 transition to well above the NH3+2 ionization threshold. The spectra were recorded at a measured resolution of 0.23 cm−1 in both a room-temperature cell (293 K) and in a slit-jet supersonic expansion (∼70 K). The absolute photoabsorption cross section with an uncertainty of ± 5% is also reported for the room-temperature spectrum. The present resolution is a factor of 10 – 100 times higher than in other recently reported broad band spectra of ammonia, and many of the observed bands show partially resolved rotational structure. We have attempted to assign this structure for a number of these bands. The oscillator strengths extracted from the data are in good agreement with previous measurements but, in the case of structured bands, the present higher resolution measurements return higher peak absorption cross sections, that increase further when the sample is cooled. The present higher resolution spectra suggest that a number of previous vibronic band assignments that were based on quantum defect considerations may require some revision. Finally, we discuss the substantial differences between the photoabsorption and photoionization data just above the first ionization threshold.
期刊介绍:
The Journal of Molecular Spectroscopy presents experimental and theoretical articles on all subjects relevant to molecular spectroscopy and its modern applications. An international medium for the publication of some of the most significant research in the field, the Journal of Molecular Spectroscopy is an invaluable resource for astrophysicists, chemists, physicists, engineers, and others involved in molecular spectroscopy research and practice.