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小木虫论坛-学术科研互动平台 » 材料区 » 无机非金属 » 交流探讨 » 发射光谱的中的Gaussian Profile是怎么得到的？
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木木Slam

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[求助] 发射光谱的中的Gaussian Profile是怎么得到的？ 已有1人参与

做的事稀土掺杂荧光粉。
很多文献做出来的PL都是非对称的，然后就会通过Gaussian Profile来进一步说明。比如Eu2+占据了LiSr4(BO3)3中的Sr的位置，通过高斯拟合就会出现子峰，通过子峰的强度高低来说明是偏短波还是长波。本来以为出峰位置是自己选的（用的origin里的Analysis-Fitting-Fit multi-peaks），但是同一个材料可能分出不一样的子峰甚至子峰数目，所以肯定是我想的不对，想请教大家。附上图片和文献。
第一篇，Fig.4的（d）图中的Inset图
As shown in Fig. 4(a), when excited by 272 nm, all samples exhibit a broad emission band covering from 520 to 750 nm. Besides, some obvious sharp peaks (at 594, 616 and 706 nm) overlapping with the broad band also can be observed. The broad band is ascribed to the 4f65d1–4f7 transitions of Eu2t. The sharp peaks are related to the characteristic emission of Eu3t, which indicates the incomplete reduction of Eu3t-Eu2t. Under the excitation by 305, 365 and 420 nm, each sample shows a broad
asymmetric emission band centered at ?620 nm, which can be seen in Fig.4(b)–(d). The emission band can be deconvoluted into two Gaussian peaks at ?613 (peak 1) and 663 nm (peak 2) (see in the inset of Fig. 4(d)), which infers the occupation of Eu2t at two different Sr2t sites. The fitting result differs from the result by Wang et al. ， which may be caused by the different synthesis processes.

第二篇，Fig.3的（a）（b）图
The blue emission band centered at 423 nm can be well decomposed into four Gaussian profiles peaking at 402(i), 436(ii), 468(iii) and 515(iv) nm, respectively. In such a case, the presence of the Gaussian peaks i, ii and iii, iv arose from the emission of Ce3t-occupancy for Sr(1) and Sr(2) sites, respectively. Based on the structural analysis above, the replacement of nearest-neighbor oxygen-richer Sr(2) by Ce3t ions (CeSr(2)) resulted in the larger crystal field splitting and the lower center of gravity of the 5d levels of Ce3t (due to covalency and nephelauxetic effect), compared to the substitution of Sr(1) by Ce3t ions (CeSr(1)). As a result, the position of the lowest 5d excited level of Ce3t is lower for CeSr(2) than that for CeSr(1). Naturally, the emission from CeSr(2) shows red-shift in comparison with that from CeSr(1). Thus, it’s reasonable that the Gaussian profiles peaking at 402(i) and 436(ii) nm are both ascribed to the 5d1 -4f1 transition of CeSr(1), and the remaining two peaks (iiiand iv) at longer wavelength are attached to that of CeSr(2). In addition, the sub-bands i and iii originate from the 5d1-2F5/2 transition of Ce3t, and the remaining two are attached to the 5d1-2F7/2 ransition of Ce3t. Corresponding to Ce3t-occupation for Sr(1) and Sr(2) sites, the energy difference between 4f ground states 2 F5/2 and 2F7/2 of Ce3t is 1939 cm1 and 2070 cm1,respectively. Both differences are in good agreement with the the theoretical value of 2000 cm1 for spin–orbit splitting between the 2F7/2 and 2F5/2 levels. The PLE and PL spectrum of single Eu2t-activated LiSr4(BO3)3 phosphors is depicted in Fig. 3(b). The excitation spectra peaking at 420 nm exhibits a broad absorption band (lem¼612 nm) from 320 to 493 nm due to the typical 4f7(8S7/2)-4f6 5d transition of Eu2t ions. Upon around 420 nm excitation, the emission spectra exhibits a single broad band with the peak at around 612 nm, which is assigned to the typical 4f65d-8S7/2 transition of Eu2t. Obviously, the broad emission band appeared to be symmetric by virtue of the superposition of two Gaussian peaks 580(v) and 646(vi) nm. The peaks v and vi correspond to 4f65d-4f7 transitions of Eu2t ions located at Sr(1) and Sr(2) sites, respectively, about which the interpretation is that it is in good accordance with Ce3t-occupation for Sr(1) and Sr(2) sites. Moreover, it is known that Eu2t ions prefer more to occupy Sr(2) sites than to occupy Sr(1) sites by the comparison of the intensity of Gaussian peaks vi and v. Besides, a significant spectral overlap is observed by the comparison between the emission band of LiSr4(BO3)3:Ce3t (see Fig. 3(a)) and the excitation band of Eu2t-activated LiSr4(BO3)3 (see Fig. 3(b)). According to Dexter0
s theory [17], it is expected that the effective resonancetype energy transfer from a sensitizer Ce3t to an activator Eu2t can occur in Ce3t/Eu2t co-doped LiSr4(BO3)3 phosphors.

第一篇：The exploration and characterization of an orange emitting long persistent luminescence phosphor LiSr4(BO3)3:Eu2+
第二篇：Potential tunable white-emitting phosphor LiSr4(BO3)3:Ce3+, Eu2+ for ultraviolet light-emitting diodes
请教大家了！！！希望有大神或者遇到这个问题的说说！！！
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1楼 2016-01-07 10:02:51
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木木Slam

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引用回帖:
5楼: Originally posted by bible2 at 2016-01-07 19:50:38
是。不然数学上分100个峰拟合的结果肯定要比99个的更准确，但是那又有啥意义呢？...

这篇文章说发射峰出现短波偏移，然后说well fitted，请问怎么看出来是well fitted了？

Figure 4b shows excitation and emission spectra of the Ba5Si8O21:Eu2+ and Ba5Si8O21:Eu2+,Dy3+ phosphors at room temperature. Under the excitation at 344 nm, both samples exhibit a broad emission from 380 to 680 nm, with an emission peak at 473 nm. The broadband emission corresponds to the spin-allowed transition from the 4f to the 5d state of Eu2+ ions, and the excitation spectra monitored at 473 nm covers a broad spectral region from 250 to 455 nm. It should be noticed that the characteristic sharp peaks of Dy3+ were not detected, which can be attributed to the electrical transitions of Dy3+, 4F9/2 → 6H13/2 for 580 nm and 4F9/2 → 6H15/2 for 486 nm, respectively.(26) It is indicated that the phosphors have only one kind of emitter that is a Eu2+ cation. As mentioned in the crystal structure of Ba5Si8O21, there are three crystallographically nonequivalent Ba2+ sites which can be substituted by the Eu2+ cation to produce three nonequivalent emission centers of Eu2+ in Ba5Si8O21. Although the 4f electrons of Eu2+ are not sensitive to their surroundings, the 5d electrons are split by the crystal field. When crystal field is weak, the emission band of Eu2+ trends to the short wavelength.(27, 28) Therefore, the asymmetric emission of Ba5Si8O21:Eu2+,Dy3+ was well fitted by three Gaussian profiles (i.e., the green profile in Figure 4b).
文献：http://pubs.acs.org/doi/full/10.1021/ic5026312
title：Sunlight Activated Long-Lasting Luminescence from Ba5Si8O21: Eu2+,Dy3+ Phosphor
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7楼2016-01-07 20:18:28
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bible2

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【答案】应助回帖

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感谢参与，应助指数 +1
木木Slam: 金币+10, ★★★很有帮助 2016-01-07 19:13:15
必须明白的前提是：分峰是一个基于物理实际的数学方法。

想必你也知道，LiSr4(BO3)3中，Sr有两个晶体学位置，Eu取代Sr。当Eu在不同位置上发光时，由于“每个”Eu周围的晶体学位置不同，“每个”Eu发光的位置也不同，（统计学上）表现为一个宽谱发射可以分为两个峰（文章1）

文章二中，Ce3+有4个峰，是因为“每个”Ce的发射峰都可分解为2D3/2→2F5/2 和 2D3/2→2F7/2这两个跃迁，2（晶体学位置）×2（跃迁），所以4个峰。

当然文章1和文章2中，Eu的分峰数据有差别，这个有几种原因，比如分峰数学处理的技巧有差异（选择的峰形不同等），测量仪器的结构有区别（光谱仪探测器的类型不同，这个可以理解为不同照相机拍出来的照片颜色肯定不是完全相同），或者是得到的数据经过的校正不同，等等。
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2楼2016-01-07 10:30:31
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木木Slam

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引用回帖:
2楼: Originally posted by bible2 at 2016-01-07 10:30:31
必须明白的前提是：分峰是一个基于物理实际的数学方法。

想必你也知道，LiSr4(BO3)3中，Sr有两个晶体学位置，Eu取代Sr。当Eu在不同位置上发光时，由于“每个”Eu周围的晶体学位置不同，“每个”Eu发光的位置也不 ...

哦。看来分峰还是自己手动的，但是要根据实际情况，是么？
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3楼2016-01-07 19:12:52
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bible2

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引用回帖:
3楼: Originally posted by 木木Slam at 2016-01-07 19:12:52
哦。看来分峰还是自己手动的，但是要根据实际情况，是么？...

是。要先通过一定的技术手段确定峰的（物理学）位置。
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4楼2016-01-07 19:48:58
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