Photochemistry can be dramatically
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Photochemistry can be dramatically different from “ordinary” chemistry See example below. Cl. Cl. Ar. Ljósefnafræði ; Dæmi / photochemistry example:. Cl. Cl. Ar. Ljósefnafræði ; Dæmi / photochemistry example:. . . . Cl. Cl. Ar. Ljósefnafræði ; Dæmi / photochemistry example:.

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Photochemistry can be dramatically

different from “ordinary” chemistry

See example below


Cl

Cl

Ar

Ljósefnafræði ; Dæmi /

photochemistry example:


Cl

Cl

Ar

Ljósefnafræði ; Dæmi /

photochemistry example:

.

.

.


Cl

Cl

Ar

Ljósefnafræði ; Dæmi /

photochemistry example:


-

+

Cl

Ar

Ljósefnafræði ; Dæmi /

photochemistry example:

Cl


Cl

Ar

Ljósefnafræði ; Dæmi /

photochemistry example:

Cl


Ljósmyndun efnahvarfa;

Nóbelsverðlaunin í efnafræði, 1999

* Sjá: http://www.hi.is/~agust/

* Sjá: http://www.hi.is/~agust/


Hr.efnahv.

Gangur og hraði efnahvarfa:

A + BC + D


Hr.efnahv.

Arrheníus: Nóbelsverðlaun 1903

Ljósmyndun efnahvarfa; Nóbelsverðlaunin í efnafræði, 1999

Gangur og hraði efnahvarfa:

A + BC + D

Hraði = k[A][B]; k = Aexp(-Ea/RT); k <= [A] vs t mælingar

Hr.efnahv.


1930-1940:

Kenning um skammlíft milliástand:

Kenning

Henry Eyring

Michael Polanyi

#

A..B

1

2

A + B

C + D

# Skammlíft milliástand:

Líftími »tími tengjasveiflu, dæmigert 10-13 – 10-12 sek

1:

2:


John C. Polanyi

Nóbelsverðlaun, 1986: Dudley Herzbach

Yuan Lee

1975-1990:

Tilraunir með sameindabunur:

Bunur

Sameinda-

buna

Árekstur

Skynjun

myndefna/

hvarfefna

Hreyfanlegur

skynjari

-Ráðið í eiginleika milliástanda út frá dreifingu / endurkasti sameinda


“Femtósekúndu litrófsgreining”

Nóbelsverðlaunin í efnafræði 1999:

Próf. Ahmed Zewail, Caltech.

1985 -

“Ljósmyndun efnahvarfa”

Ljosm.

Þ.e. Gleypnimælingar milliástanda vs tími fyrir tíma(bil) £10-12 s:

Gleypnimælingar

með ljósleiftrum

10-15 s

AB

CD

A . .B

C ..D

A + B

0,000000000000001 s

C + D


Verðl.


http://www.its.caltech.edu/~femto/

Femtol.


Of margbreytilegt

/flókið

Hvernig / Hvað?

Hvernig?

A + BC + D

Öll stig hvarfsins koma fyrir samtímis, þ.e.:


Dæmi: “½ hvarf”, sbr.: ICN# I + CN, Þ.e.:

I

CN#

Skapa þarf “samhæfðar aðstæður”:


Dæmi: “½ hvarf”, sbr.: ICN# I + CN, Þ.e.:

Gleypnimælingar

ICN#

I +CN

ICN#

Myndað með femtó-

sekúndu LASER-púls

gleypni

ICN

Skapa þarf “samhæfðar aðstæður”:

½ hvarf

I

CN


Framkvæmd:

ICN-Tilr.


Gleypni-

Mælingar:

Niðurstöður:

Nánar:

ICN#

I +CN

ICN-niðurst.

ICN


(a)

(b)

[NaI#Na..I# ]Na + I

NaI

NaI

(a)

NaI#

(b)

Na


Stilbene(1)


Stilbene(2)


IH..OCO [I..H..O..CO]I+HO+CO

IH+OCO

Van der

Waals

“Sameindir”

Spýtt-

kæling

Sameinda-

buna


Cyclob.

C4H8C4H8#C2H4 + C2H4

???


Rofnun tetrafluordijoðetans:

C2F4I2

C2F4I2C2F4 + 2I:

.

I

F

I

F

F

?(1)

F

C C

C C

F

.

F

F

I

F

I

.

I

F

F

I

F

I

F

F

.

F

?(2)

C C

C C

C C

.

F

.

F

F

I

F

I

F

F

I


mynataka


5


6


7


8


9


10


Reactioncrosssection:

A + M ???

M1 + M2 ???

A + B C + D


Cross section = s = <d>2p

Reactioncrosssection:

A + M ???

M1 + M2 ???

A + B C + D

d

But ions:


+

+

-

-

-

+

-

+

+

+

F µ 1/r2

But ions:

Reactioncrosssection:

A+ + B C + D


+

+

-

-

-

+

-

+

+

+

But Ions:

Reactioncrosssection:

A+ + B C + D


+

+

But ions:

Reactioncrosssection:

A+ + B C + D

Collision frequency much larger


Ions:

+

Collision cross

section =

s >> <d>2p

Reactioncrosssection:

A + M ???

M1 + M2 ???

A + B C + D

d


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