Detection of Recurrent Fluorescence Photons

Ebara, Yuta; Furukawa, T.; Matsumoto, Jun; Tanuma, H.; Azuma, T.; Shiromaru, H.; Hansen, Klavs

doi:10.1103/physrevlett.117.133004

Cited by 46 publications

(38 citation statements)

References 27 publications

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“…The latter process can occur on a much more rapid timescale ( 2 × 10 −5 s ; Chandrasekaran et al 2014) than the slow emission of mid-infrared vibrational photons ( 3s), but it requires a highly vibrationally excited ground state and the presence of a low-lying electronic state with excitation energy E 2.3 eV above ground and a high transition probability to the ground state. The detection of red photons resulting from recurrent fluorescence in C − 6 ions was recently reported by Ebara et al (2016), confirming experimentally the viability of this process. More recently, recurrent fluorescence photons from C − 4 have also been demonstrated experimentally (Yoshida et al 2017).…”

Section: Introductionsupporting

confidence: 68%

Are the carriers of diffuse interstellar bands and extended red emission the same?

Lai

Witt

Álvarez

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We report the first spectroscopic observations of a background star seen through the region between the ionization front and the dissociation front of the nebula IC 63. This photodissociation region (PDR) exhibits intense extended red emission (ERE) attributed to fluorescence by large molecules/ions. We detected strong diffuse interstellar bands (DIB) in the stellar spectrum, including an exceptionally strong and broad DIB at λ4428. The detection of strong DIBs in association with ERE could be consistent with the suggestion that the carriers of DIBs and ERE are identical. The likely ERE process is recurrent fluorescence, enabled by inverse internal conversions from highly excited vibrational levels of the ground state to low-lying electronic states with subsequent transitions to ground. This provides a path to rapid radiative cooling for molecules/molecular ions, greatly enhancing their ability to survive in a strongly irradiated environment. The ratio of the equivalent widths (EW) of DIBs λ5797 and λ5780 in IC 63 is the same as that observed in the low-density interstellar medium with UV interstellar radiation fields (ISRF) weaker by at least two orders of magnitude. This falsifies suggestions that the ratio of these two DIBs can serve as a measure of the UV strength of the ISRF. Observations of the nebular spectrum of the PDR of IC 63 at locations immediately adjacent to where DIBs were detected failed to reveal any presence of sharp emission features seen in the spectrum of the Red Rectangle nebula. This casts doubts upon proposals that the carriers of these features are the same as those of DIBs seen at slightly shorter wavelengths.

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Section: Introductionsupporting

confidence: 68%

Are the carriers of diffuse interstellar bands and extended red emission the same?

Lai

Witt

Álvarez

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Inverse internal conversion turns an initially large reservoir of vibrational energy into electronic excitation in systems where low-lying electronic states exist. Only recently has it been possible to experimentally confirm RF by measuring the critical rate coefficients in C − 6 (Chandrasekaran et al 2014;Martin et al 2013) and by observing the resulting red photons (Ebara et al 2016). It is an intrinsic characteristic of RF that its expected photon conversion efficiencies increases with a growing energy difference between that of the exciting photon and the resultant fluorescence photons, a behaviour totally opposite to that seen in classical fluorescence or photoluminescence.…”

Section: The Ere Emission Process and Ere Carrier Modelsmentioning

confidence: 99%

“…Moreover, the energy difference between exciting and emitted photons for optimum photon conversion efficiency, the Stokes shift, is typically of order 1 eV or less. On the other hand, recurrent fluorescence (Leger et al 1988;Duley 2009) in highly isolated molecules or molecular ions relies on inverse internal conversion of vibrational energy into excitation energy of low-lying electronic states (Nitzan & Jortner 1979;Martin et al 2013;Chandrasekaran et al 2014;Ebara et al 2016). This process results in the possible emission of more than one photon, following excitation by the absorption of a single photon of sufficiently high energy.…”

Section: Introductionmentioning

confidence: 99%

Extended red emission in IC59 and IC63

Lai¹,

Witt²,

Crawford³

2017

Monthly Notices of the Royal Astronomical Society

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We analysed new wide-field, wide-and narrow-band optical images of IC 59 and IC 63, two nebulae which are externally illuminated by the early B-star γ Cas, with the objective of mapping the extended red emission (ERE), a dust-related photoluminescence process that is still poorly understood, in these two clouds. The spatial distribution of the ERE relative to the direction of the incident radiation and relative to other emission processes, whose carriers and excitation requirements are known, provides important constraints on the excitation of the ERE. In both nebulae, we find the ERE intensity to peak spatially well before the more extended distribution of midinfrared emission in the unidentified infrared bands, supporting earlier findings that point toward far-ultraviolet (11 eV < E photon < 13.6 eV) photons as the source of ERE excitation. The band-integrated absolute intensities of the ERE in IC 59 and IC 63 measured relative to the number density of photons available for ERE excitation are lower by about two orders of magnitude compared to ERE intensities observed in the high-latitude diffuse interstellar medium (ISM). This suggests that the lifetime of the ERE carriers is significantly reduced in the more intense radiation field prevailing in IC 59 and IC 63, pointing toward potential carriers that are only marginally stable against photo-processing under interstellar conditions. A model involving isolated molecules or molecular ions, capable of inverse internal conversion and recurrent fluorescence, appears to provide the most likely explanation for our observational results.

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“…This type of radiation was proposed a long time ago [32,33] but was only recently detected for several excited carbon species [19,25,34,35] and very recently also confirmed by direct detection of emitted photons for C 6 − [36].…”

Section: Fig 4 Fits Of the Radiative Cooling Time Constant With Eqmentioning

confidence: 99%

Thermal radiation of gold clusters on microsecond time scales

et al. 2017

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Small positively charged gold clusters have been found to emit thermal radiation at a very high rate, with time constants ranging from one to 35 μs for Au n + (n = 6-13,15). For sizes n = 14,16-20 the radiation occurs on much longer time scales. Strong thermal suppression of the population of higher-lying states puts constraints on the possible energies of excited states that can contribute to the radiation. Taking that into account, an evaluation of the experimentally determined rate constants shows that the strong radiation originates from thermally excited low-lying electronic states hitherto not observed. The origin of these states is discussed and two possibilities are suggested: one is related to electron correlation and electron pairing, and the other results from thermal shape fluctuations.

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Detection of Recurrent Fluorescence Photons

Cited by 46 publications

References 27 publications

Are the carriers of diffuse interstellar bands and extended red emission the same?

Are the carriers of diffuse interstellar bands and extended red emission the same?

Extended red emission in IC59 and IC63

Thermal radiation of gold clusters on microsecond time scales

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