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五元素復合空心陰極燈
特點
用于原子吸收的配(pei)套(tao)光源,具有(you)譜線發射能量強、吸收靈敏度高、穩定性好、壽(shou)命長(大部(bu)分(fen)元素(su)都可達到5000mAh,低熔點(dian)元素(su)可達3000mAh)、低噪聲、低漂移等特性。
五元素復合空心陰極燈
五元素復合空心陰極燈
發光(guang)原理(li)
空(kong)心陰(yin)(yin)極(ji)燈(hollow cathode lamp,HCL)是一種特(te)殊形式的(de)(de)低(di)壓氣(qi)(qi)體放電(dian)(dian)(dian)光(guang)源,放電(dian)(dian)(dian)集中(zhong)(zhong)于陰(yin)(yin)極(ji)空(kong)腔(qiang)內(nei)。當在兩極(ji)之間施加200V-500V電(dian)(dian)(dian)壓時(shi),便產生(sheng)輝光(guang)放電(dian)(dian)(dian)。在電(dian)(dian)(dian)場作用下(xia),電(dian)(dian)(dian)子(zi)(zi)(zi)在飛向陽極(ji)的(de)(de)途中(zhong)(zhong),與(yu)載氣(qi)(qi)原(yuan)(yuan)子(zi)(zi)(zi)碰撞并(bing)使之電(dian)(dian)(dian)離(li),放出二次電(dian)(dian)(dian)子(zi)(zi)(zi),使電(dian)(dian)(dian)子(zi)(zi)(zi)與(yu)正(zheng)離(li)子(zi)(zi)(zi)數目增(zeng)加,以(yi)維持放電(dian)(dian)(dian)。正(zheng)離(li)子(zi)(zi)(zi)從(cong)電(dian)(dian)(dian)場獲得動(dong)能(neng)。如(ru)果正(zheng)離(li)子(zi)(zi)(zi)的(de)(de)動(dong)能(neng)足以(yi)克(ke)服金屬陰(yin)(yin)極(ji)表面(mian)的(de)(de)晶格(ge)(ge)能(neng),當其撞擊在陰(yin)(yin)極(ji)表面(mian)時(shi),就可以(yi)將原(yuan)(yuan)子(zi)(zi)(zi)從(cong)晶格(ge)(ge)中(zhong)(zhong)濺射出來。除濺射作用之外,陰(yin)(yin)極(ji)受熱也要導致陰(yin)(yin)極(ji)表面(mian)元(yuan)素(su)的(de)(de)熱蒸發(fa)。濺射與(yu)蒸發(fa)出來的(de)(de)原(yuan)(yuan)子(zi)(zi)(zi)進入空(kong)腔(qiang)內(nei),再(zai)與(yu)電(dian)(dian)(dian)子(zi)(zi)(zi)、原(yuan)(yuan)子(zi)(zi)(zi)、離(li)子(zi)(zi)(zi)等(deng)發(fa)生(sheng)第二類碰撞而受到激發(fa),發(fa)射出相應(ying)元(yuan)素(su)的(de)(de)特(te)征的(de)(de)共振輻射。與(yu)此同(tong)時(shi),HCL所發(fa)射的(de)(de)譜(pu)線中(zhong)(zhong)還包含了內(nei)充氣(qi)(qi)、陰(yin)(yin)極(ji)材(cai)料(liao)和雜質元(yuan)素(su)等(deng)譜(pu)線。
因為(wei)燈(deng)(deng)內填(tian)充氣體壓力低,壓力變(bian)寬很小;陰極溫度(du)較低,熱變(bian)寬也很小;同時(shi),因為(wei)氣體密度(du)低,自吸變(bian)寬也不存在。HCL基本滿足發射(she)譜(pu)線(xian)(xian)(xian)的(de)半(ban)寬度(du)窄(zhai)、譜(pu)線(xian)(xian)(xian)強度(du)大(da)且穩(wen)定(ding)、譜(pu)線(xian)(xian)(xian)背(bei)景小、操作方便和經(jing)久耐(nai)用(yong)(yong)等銳線(xian)(xian)(xian)光源(yuan)的(de)基本要求。并(bing)且,當采用(yong)(yong)較大(da)的(de)燈(deng)(deng)電流(liu)時(shi),HCL所發射(she)譜(pu)線(xian)(xian)(xian)半(ban)寬度(du)變(bian)寬和譜(pu)線(xian)(xian)(xian)強度(du)增高,此時(shi)檢測器(qi)的(de)負高壓降低,吸光度(du)讀(du)數(shu)穩(wen)定(ding)。
五元素復合空心陰極燈
大多數(shu)為純金屬或合金,對于一(yi)些貴金屬,則將其制成薄片襯在支持(chi)電極(ji)上。陰極(ji)在中間為空(kong)桶形狀,空(kong)心陰極(ji)燈因此(ci)得名
陽極(ji)
為一焊有鉭片或鈦(tai)絲的鎢棒,因(yin)為鉭片或鈦(tai)絲具有吸氣作用,在高溫下可以吸收少量有害氣體(如H2)。
屏(ping)蔽(bi)層
為防止陰陽(yang)極(ji)的(de)擊穿,在陰陽(yang)極(ji)間設有屏蔽層(ceng)。
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