Spectrophotometry Notes PDF
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These notes cover spectrophotometry, a crucial analytical technique in chemistry. Details on the electromagnetic spectrum, light interaction, and types of transitions are described. The focus is on the fundamental principles rather than specific applications or problems.
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Spectrophotometry: spectro- = spectrum photo- = light or photon - metry = measurement {measuring light spectrum} It is one of the instrumental methods of...
Spectrophotometry: spectro- = spectrum photo- = light or photon - metry = measurement {measuring light spectrum} It is one of the instrumental methods of analysis that depends on measuring the interaction between electromagnetic radiation (EMR) and molecules or atoms. It is used for structural and quantitative analysis of substances. Colorimetry (Visible Spectrophotometry): It is a branch of spectrophotometry in which the spectrophotometric measurement is performed in the visible region of light. Electromagnetic radiation (EMR): It is a form of energy that consists of 2 fields, electric field & magnetic field, and both are perpendicular to each other and perpendicular to the direction of the radiation propagation. Light is a type of electromagnetic radiations. 58 (OHFWURPDJQHWLF6SHFWUXP 7KH HOHFWURPDJQHWLFVSHFWUXP LVWKHGLVWULEXWLRQRI HOHFWURPDJQHWLF UDGLDWLRQ DFFRUGLQJWRHQHUJ\DQGZDYHOHQJWK 8OWUDYLROHWUHJLRQ § – QP 9LVLEOHUHJLRQ § – QP 5HPHPEHU - QDQRPHWHU QP P $QJVWURP c -P 3URSHUWLHVRIHOHFWURPDJQHWLFUDGLDWLRQ (05 1. :DYHOHQJWK Ȝ³/DPEGD´ WKHOLQHDUGLVWDQFHEHWZHHQVXFFHVVLYHPD[LPDRU PLQLPDRIDZDYH>8QLWV QPc««HWF@ 2. )UHTXHQF\ Ȟ³1X´ WKHQXPEHURIZDYHVSHUVHFRQGRUWKHQXPEHURIF\FOHV RU RVFLOODWLRQV SHU VHFRQG >8QLWV V- RU +HUW] +] @ +] PHDQV F\FOH SHU VHFRQG 59 3.:DYHQXPEHU Nj ³1X EDU´ WKH QXPEHU RI ZDYHV SHU FHQWLPHWHU DQG LW LV HTXDOWRWKHUHFLSURFDORIZDYHOHQJWKH[SUHVVHGLQFHQWLPHWHU Ȝ >8QLWV FP-@ 4. 7KHYHORFLW\RIOLJKW IUHTXHQF\[ZDYHOHQJWK F ȞȜ 7KHYHORFLW\RIOLJKWLQYDFXXP F HTXDOV[ NPV 7KHIUHTXHQF\ Ȟ LVLQYHUVHO\SURSRUWLRQDOWRWKHZDYHOHQJWK Ȝ 5. 7KHHQHUJ\ ( RIDVLQJOHSKRWRQ ( KȞZKHUH³K´LV3ODQFN¶VFRQVWDQW KFȜZKHUH³F´LVOLJKWYHORFLW\ (ĮȞDQG(ĮȜ 7KHKLJKHULVWKHZDYHOHQJWKWKHORZHULVWKHIUHTXHQF\ WKHORZHULVWKHHQHUJ\ ĹȜŁĻȞŁĻ( DQG ĻȜŁĹȞŁĹ( 89OLJKW LVPRUHHQHUJHWLFWKDQ YLVLEOHOLJKW DQGWKDQ ,5 6R89OLJKWLVPRUHGDQJHURXVWRWKHERG\WKDQYLVLEOHOLJKWDQG,5 ,QWHUDFWLRQRIOLJKWZLWKPDWWHU ,WLQFOXGHVWKHSURFHVVHVRI$EVRUSWLRQDQG(PLVVLRQ :KHQPROHFXOHVDUHVXEMHFWHGWROLJKWVRPHRIWKHPDEVRUEDSRUWLRQRIWKHOLJKWDQGDV DUHVXOWFHUWDLQHOHFWURQVZLWKLQWKHPROHFXOHVXQGHUJRDWUDQVLWLRQIURPWKHJURXQGVWDWH ORZHUHQHUJ\OHYHO WRH[FLWHGVWDWH KLJKHUHQHUJ\OHYHO ^$EVRUSWLRQ` 60 7KHQ WKH HOHFWURQV UHWXUQ IURP WKH KLJKHU HQHUJ\ OHYHO WR WKH ORZHU HQHUJ\ OHYHO UHOD[DWLRQ DQGWKLVSURFHVVPD\EHDVVRFLDWHGZLWKHPLVVLRQRIOLJKWRIRQO\FHUWDLQ FKDUDFWHULVWLFZDYHOHQJWKV ^(PLVVLRQ` Types of Transitions ¾ σ → σ* transition: Electrons in σ orbitals form single bonds, and thus to be excited to the į* they needs very high energy.ERQGEUHDNLQJ ,
