Ultabrza tranzijentna apsorpcija fotokemijskih reakcija

master's thesis

• Title (english): Ultrafast transient absorption of photochemical reactions
• Author: Mateo Forjan
• Mentor: Silvije Vdović (mentor)
• Mentor: Željko Skoko (mentor)
• Committee member: Željko Skoko (predsjednik povjerenstva)
• Committee member: Silvije Vdović (član povjerenstva)
• Committee member: Krešimir Kumerički (član povjerenstva)
• Committee member: Nikola Poljak (član povjerenstva)
• Committee member: Marinko Jablan (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2018-06-26, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

U ovom diplomskom radu metodom ultrabrze tranzijentne apsorpcije proučena je ultrabrza dinamika molekule rodamina B (C28H31ClN2O3) te dvolomnost inducirana Kerr efektom u benzenu i otopini vode i acetonitrila (C2H3N). Molekule rodamina B otopljene u acetonitrilu pobudivane su femtosekundnim laserskim pulsevima valne duljine 267nm (pumpni puls) dok je njihova apsorpcija kao funkcija vremena ispitivana probnim pulsevima čiji je spektar superkontinuum generiran u kalcij-fluoridnoj (CaF2) pločici. Mjerenjima je dobiven signal koji se sastojao od pozitivnog i negativnog dijela. Pozitivan dio uzrokovan je apsorpcijom višeg stanja u koje su molekule pobudene pumpnom zrakom dok je negativan signal uzrokovan stimuliranom emisijom i izbjeljivanjem osnovnog stanja što je zaključeno promatranjem emisijske i apsorpcijske krivulje molekule rodamina B. Mjerenjem dvolomnosti inducirane Kerr efektom proučeno je trajanje te raspored spektralnih komponenti probnog pulsa u vremenu. Zaključeno je da je puls uvelike proširen u vremenu u odnosu na fundamentalni te da posjeduje pozitivan cvrkut. Uz spomenute rezultate prikazani su i superkontinuumi dobiveni u safirnoj i CaF2 pločici. Dobiveni rezultati pokazuju da je korišteni postav moguće koristiti za buduća proučavanja raznih uzoraka metodom ultrabrze tranzijentne apsorpcije.

Abstract (english)

In this thesis, ultrafast dynamics of rhodamine B (C28H31ClN2O3) was studied by measuring time-resolved absorption changes using ultrafast transient absorption spectroscopy technique. In addition, birefringence induced by Kerr effect was studied in benzene and a 50:50 mixture of water and acetonitrile (C2H3N). Rhodamine B molecules dissolved in acetonitrile were excited by femtosecond pulses with the wavelength of 267nm (pump pulse) while their absorption as a function of time was tested with the probe pulses. Probe pulse spectrum was supercontinuum generated in calcium-fluoride (CaF2) crystal. Resulting signal consisted of positive and negative contribution. Positive contribution of the signal was caused by excited state absorption in which the molecules were excited by the pump beam. Negative contribution of the signal was caused by stimulated emission and ground state bleach which was concluded by observation of emission and absorption spectrum of rhodamine B. Spectral and temporal characteristics of probe pulses were studied by measurements of birefringence induced by Kerr effect. It was concluded that the probe pulses were significantly broadened in time in comparison to the fundamental pulses and also, positive chirp was present in probe pulses. In addition to above mentioned results, supercontinua generated in sapphire and CaF2 crystals were shown. Obtained results proved the functionality of the used experimental setup which will be used for future research and ultrafast transient absorption measurements of many different samples.

• Keywords: femtosekundni laser; femtosekundni pulsevi; ultrabrza tranzijentna apsorpcija; Kerr efekt; inducirana dvolomnost; superkontinuum
• Keywords (english): femtosecond laser; femtosecond pulses; ultrafast transient absorption; Kerr effect; induced birefringence; supercontinuum
• Language: croatian
• URN:NBN: urn:nbn:hr:217:738836
• Study programme: Title: Physics; specializations in: Research; Course: Research; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-07-17 14:43:18