Photochemistry

hn

OOOOO

O

OOOOO

hn T1

Photochemistry

O

OOOOO

hn

C

CC

H

H

O

H

H

C

CC

H

H

O

H

H

Acrolein

T1

Photochemistry

T(n,p*)

T(p,p*)

P.E.

Twisting coordinate

C C

C

H

H O

H H

O

C C

C

H

H

H

H

T1(n,p*)

T1(p,p*)

P.E.

Twisting coordinate

C C

C

H

H O

H H

O

C C

C

H

H

H

H

T1 T1T2 T2

T1(n,p*)

T1(p,p*)

C C

C

H

H O

H H

O

C C

C

H

H

H

H

T1 T1T2 T2

S0

S1(n,p*)

415 410 405 400 395 390 3850.0

0.5

1.0

0

5

10

15

20

25

Abs

orba

nce

Wavelength, nm ,

M -1

cm

-1

O

O

T1(n,p*)← S0

S1(n,p*)← S0

Survey at 0.05-nm resolution (Cary-5E)Acrolein (84 T) in 10-cm cell at room temperature1

1Prof. William Polik, Hope College

415 410 405 400 395 390 3850.0

0.5

1.0

0

5

10

15

20

25

Abs

orba

nce

Wavelength, nm ,

M -1

cm

-1

O

O

O

T1(n,p*)← S0

S1(n,p*)← S0

S1(n,p*)← S0

Survey at 0.05-nm resolution (Cary-5E)Acrolein (84 T) in 10-cm cell at room temperature1

1Prof. William Polik, Hope College

Dye Laser

Telescope

Ringdown CellPhotomultiplier

OscilloscopeComputer

Nd:YAG Laser10 Hz

355 nm385 nm,

0.2 mJ/pulse

50 W

Dye Laser

Telescope

Ringdown CellPhotomultiplier

OscilloscopeComputer

Nd:YAG Laser10 Hz

355 nm385 nm,

0.2 mJ/pulse

50 W

Jordan Valve

415 410 405 400 395 390 3850.0

0.5

1.0

0

5

10

15

20

25

Abs

orba

nce

Wavelength, nm ,

M -1

cm

-1

O

O

O

T1(n,p*)← S0

S1(n,p*)← S0

S1(n,p*)← S0

Survey at 0.05-nm resolution (Cary-5E)Acrolein (84 T) in 10-cm cell at room temperature1

1Prof. William Polik, Hope College

412 410 408 406

Wavelength (nm)

CRD Survey Spectrum

O

O

T1(n,p*)← S0 S1(n,p*)← S0

Room Temp

000 00

0

412 410 408 406

Wavelength (nm)

O

O

T1(n,p*)← S0 S1(n,p*)← S0

CRD Survey Spectrum

Room Temp

Jet-Cooled

000 00

0

412 410 408 406

Wavelength (nm)

O

O

T1(n,p*)← S0 S1(n,p*)← S0

CRD Survey Spectrum

Room Temp

Jet-Cooled

000 00

0

24200 243000.0

0.1

0.2

0.3

0.4

0.5

0.6

0

5

10

15

20

25

30

414 413 412 411 P

hoto

n Lo

ss p

er P

ass

(par

ts p

er th

ousa

nd)

Mol

ar A

bsor

ptiv

ity

(dm

3 mol

1 c

m1

)

Wavenumber, cm1

Wavelength (nm)

T1(n,p*)← S0

000 band

24200 243000.0

0.1

0.2

0.3

0.4

0.5

0.6

0

5

10

15

20

25

30

414 413 412 411 P

hoto

n Lo

ss p

er P

ass

(par

ts p

er th

ousa

nd)

Mol

ar A

bsor

ptiv

ity

(dm

3 mol

1 c

m1

)

Wavenumber, cm1

Wavelength (nm)

24200 24300

414 413 412 411

Wavenumber, cm1

Wavelength (nm)

T1(n,p*)← S0

000 band

Hund’s Case (b)

NJ

S

DJ= ±1DN=0, ±1, ±2

N″=1

N′=3

J″=1

N′=2J′=1J′=2J′=3

J′=2J′=3J′=4

N′=1J′=0J′=1J′=2

T1

S0

NJ

S

b

a c

DJ= 0, ±1DKa= 0, ±1, ±2DN=0, ±1, ±2

DJ= ±1DN=0, ±1, ±2

Singlet-Triplet Selection Rules

Erot ≈ BN(N+1) + Ka2(A – B)

NJ

S

b

a c

DJ= 0, ±1DKa= 0, ±1, ±2DN=0, ±1, ±2

DJ= ±1DN=0, ±1, ±2

Singlet-Triplet Selection Rules

Erot ≈ BN(N+1) + Ka2(A – B)

24200 243000.0

0.1

0.2

0.3

0.4

0.5

0.6

0

5

10

15

20

25

30

414 413 412 411 P

hoto

n Lo

ss p

er P

ass

(par

ts p

er th

ousa

nd)

Mol

ar A

bsor

ptiv

ity

(dm

3 mol

1 c

m1

)

Wavenumber, cm1

Wavelength (nm)

24200 24300

414 413 412 411

Wavenumber, cm1

Wavelength (nm)

T1(n,p*)← S0

000 band

24200 243000.0

0.1

0.2

0.3

0.4

0.5

0.6

0

5

10

15

20

25

30

414 413 412 411 P

hoto

n Lo

ss p

er P

ass

(par

ts p

er th

ousa

nd)

Mol

ar A

bsor

ptiv

ity

(dm

3 mol

1 c

m1

)

Wavenumber, cm1

Wavelength (nm)

24200 24300

414 413 412 411

Wavenumber, cm1

Wavelength (nm)

T1(n,p*)← S0

000 band

Hot bands

24240 24260

412.6 412.4 412.2

Wavenumber, cm1

Wavelength (nm)

Room Temp

Jet-Cooled

24240 24260

412.6 412.4 412.2

Wavenumber, cm1

Wavelength (nm)

Jet-Cooled

b

a c

𝑩 ′<𝑩}            } ^ {′} > 𝑨 𝑨 ¿¿

Erot ≈ BN(N+1) + Ka2(A – B)

24240 24260

412.6 412.4 412.2

Wavenumber, cm1

Wavelength (nm)

Jet-Cooled

b

a c

𝑩 ′<𝑩}            } ^ {′} > 𝑨 𝑨 ¿¿

K″ = 01 2 3 4… sub-band origins,DKa =0

Erot ≈ BN(N+1) + Ka2(A – B)

24240 24260

412.6 412.4 412.2

Wavenumber, cm1

Wavelength (nm)

𝑩 ′<𝑩}            } ^ {′} > 𝑨 𝑨 ¿¿

K″ = 3

Sub-band head,DN = +2, N″ ~ 45

Jet-Cooled

STROTA1

1Richard Judge et al.

Erot ≈ BN(N+1) + Ka2(A – B)

24240 24260

412.6 412.4 412.2

Wavenumber, cm1

Wavelength (nm)

𝑩 ′<𝑩}            } ^ {′} > 𝑨 𝑨 ¿¿

5

67

8

K″ = 3

Jet-Cooled

DKa=0, DN=+2

STROTA

Erot ≈ BN(N+1) + Ka2(A – B)

24235 24240 24245 24250 24255 24260 24265 24270

Wavenumber (cm1)

STROTA

24235 24240 24245 24250 24255 24260 24265 24270

Wavenumber (cm1)

Ka″ = 3heads

5

67

8

Ka″ = 8head

9

10

DN=+1 DN=+2

4

Ka″ = 3heads

5

67

8

DN=+2

A″ = 1.580 cm–1

B″ = 0.1554 cm–1

C″ = 0.1415 cm–1

A′ = 1.662 cm–1

B′ = 0.1485 cm–1

C′ = 0.1363 cm–1

24235 24240 24245 24250 24255 24260 24265 24270

Wavenumber (cm1)

Ka″ = 8head

9

10

DN=+1

T1(n,p*)Microwave Spectroscopy

A″ = 1.580 cm–1

B″ = 0.1554 cm–1

C″ = 0.1415 cm–1

A′ = 1.662 cm–1

B′ = 0.1485 cm–1

C′ = 0.1363 cm–1

24220 24240 24260 24280

Wavenumber (cm-1)

Room Temp

Jet-Cooled

T1(n,p*)

exp

sim

sim

exp

Microwave Spectroscopy

A″ = 1.580 cm–1

B″ = 0.1554 cm–1

C″ = 0.1415 cm–1

A′ = 1.662 cm–1

B′ = 0.1485 cm–1

C′ = 0.1363 cm–1

24230 24240 24250 24260

Wavenumber (cm-1)

Trot = 63 KGLor = 0.20 cm-1

T1(n,p*)

exp

sim

Microwave Spectroscopy

A″ = 1.580 cm–1

B″ = 0.1554 cm–1

C″ = 0.1415 cm–1

A′ = 1.662 cm–1

B′ = 0.1485 cm–1

C′ = 0.1363 cm–1

24230 24240 24250 24260

Wavenumber (cm-1)

Trot = 63 KGLor = 0.20 cm-1

T1(n,p*)t = 25 ps

T1(n,p*)

exp

sim

Microwave Spectroscopy

A″ = 1.580 cm–1

B″ = 0.1554 cm–1

C″ = 0.1415 cm–1

A′ = 1.662 cm–1

B′ = 0.1485 cm–1

C′ = 0.1363 cm–1

24230 24240 24250 24260

Wavenumber (cm-1)

Trot = 63 KGLor = 0.20 cm-1

T1(n,p*)t = 25 ps

T1(n,p*)

exp

sim

S1(n,p*)1

t = 2 ps

1K.W. Paulisse et al., J. Chem. Phys. v. 113, p. 184 (2000).

Microwave Spectroscopy

T1(n,p*)

T1(p,p*)

C C

C

H

H O

H H

O

C C

C

H

H

H

H

T1 T1T2 T2

S0

S1(n,p*)

Acknowledgements

• NSF (CHE-0848615)

• Camille and Henry Dreyfus Foundation, Inc.(Henry Dreyfus Teacher-Scholar Award)

• Prof. Richard Judge (UW-Parkside)

• Prof. William Polik (Hope College)