Supplementary material for Vibrational Spectra of Four Polycyclic Aromatic Hydrocarbons Under High
Pressure: Implications for Stabilities of PAHs during Accretion
Earl O’Bannon III and Quentin Williams
Department of Earth and Planetary Sciences, University of California, Santa Cruz, CA 95064, U.S.A.
Color Change and Luminescence as a Function of Pressure
At ambient pressure and temperature, naphthalene, anthracene, and phenanthrene are each white as powders, and clear and transparent when compacted, while pyrene is slightly yellow as a result of its more extended aromatic system. All of the aromatic compounds studied exhibit a color change as pressure is increased, from yellow to orange to red, dark red, and finally black (Figure S1). The color change is partially reversible on decompression, even if irreversible structural changes occurred, as manifested within the infrared or Raman spectra. However, none of the PAHS return to white/clear on decompression: during our infrared analysis of the recovered high-pressure products, all samples were yellow to red upon decompression. In the case of anthracene (Figure S1), when it was decompressed to room pressure the color changed back to a light yellow: this is the closest to a fully reversible color change of any of these PAHs. Color changes in PAHs are likely associated with pressure-induced changes in π-π interactions. Citroni et al. (2008) state that the π- orbitals are more pressure sensitive than  orbitals due to their smaller overlap at atmospheric conditions. Cross-linking between molecules within the structure disturbs the πelectron distribution and decreases the portion of the original molecule over which the π electrons are mobile, and this electronic change has been associated with the pressure-induced color changes in these molecules (Aust et al.
1964).
Pressure-induced luminescence is encountered in all of the PAHs studied at pressures that correspond to those where the inter-molecular bands begin to shift at rates similar to the lowest lying intra-molecular bands, and well below the pressures at which the PAHs amorphize. Only one type of electronic transition is expected in the visible and near UV regions in PAHs, which is the π-π* transition ( Krasovitskii and Bolotin, 1988). Thus, the pressure-induced onset of luminescence provides direct evidence of increasing overlap of π-orbitals at high pressure, and could also provide indirect evidence of dimerization/cross-linking. When dimers form, the energy difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in
PAHs is decreased. When the HOMO-LUMO energy gap is reduced through pressure-induced dimerization, laser
1

excitation at 633 nm can excite an electron into the LUMO. This visible excitation is not observed at room pressure, where wavelengths of 265 nm for naphthalene, 253.7 nm for anthracene, 253.7 nm for phenantrene, and 313.0 nm for pyrene, respectively, are required to access this transition ( Krasovitskii and Bolotin, 1988). As pressure increases, the energy gap between the HOMO and LUMO continues to decrease, and the absorption and hence luminescence become more intense. Pressure-induced luminescence initially obscures the Raman C-H stretching vibrations in all PAHs studied, and eventually prevents any Raman spectral features from being observed.
Decompression Spectra
Decompression spectra were collected for all of the PAHs studied in both the Raman (Figure S2a-d) and infrared (Figure S3a-d). Spectral features did not return on decompression in the Raman except for within anthracene. Collecting Raman spectra on decompression was difficult, likely due to the disordered nature of the sample and the increased luminescence background on decompression. For anthracene, most of the Raman modes reappeared on decompression, but not all, suggesting that subtle irreversible changes occurred on compression to
~10 GPa. C-H stretches and bending vibrations were not observed in the infrared decompression spectra of any of the PAHs studied. C-C stretches and bending modes are not observed in the infrared decompression spectra of naphthalene (Figure S3a) and anthracene (Figure S3b), but they are observed in phenanthrene (Figure S3c) at ~732 and ~821 cm -1 suggesting that some portion of its aromatic rings are likely still intact after compression to ~13 GPa.
Hence, pressures greater than ~13 GPa appear required to break C-C bonds in the aromatic rings of phenanthrene. A mode at ~729 cm -1 is observed in the infrared decompression spectra of anthracene: however, this band does not correspond to any mode observed prior to compression. This mode is likely associated with a C-C stretch or bend, and its different frequency on decompression suggests that the anthracene structure is highly disordered after compression to ~20 GPa. Two broad modes at ~707 and 837 cm -1 are observed in the decompression spectra of pyrene. These modes correspond to a C-H bend and C-C stretch, respectively, and are ~2 cm -1 lower than they are observed at room pressure and temperature prior to compression. The appearance of these broadened and slightly shifted modes suggests that the long-range order of pyrene has been lost and replaced with a wider variety of local environments. The variable appearances of C-H bends and aromatic C-C stretches in highly disordered or amorphous carbonaceous material could be useful in determining which PAH was the pre-disordering protolith.
Infrared and Raman Modes of all PAHs studied
Observed infrared and Raman modes, pressure shifts of the modes, and mode Gr ü neisen parameters up to
2

the first phase transition as well as the high-pressure modes, pressure shift of those modes, and high-pressure mode
Gr ü neisen parameters for each individual PAH studied are listed in Tables S1 through S4.
References
Aust RB, Bentley WH, Drickamer HG (1964) Behavior of fused ring aromatic hydrocarbons at very high pressure. J
Chem Phys , 41, 1856-1864.
Citroni M, Bini R, Foggi P, Schettino V (2008) Role of excited electronic states in the high-pressure amorphization of benzene. Proc Natl Acad Sci USA , 105 , 7658-7663.
Krasovitskii BM, Bolotin BM (1988). Organic luminescent materials. Wiley-VCH.
3

Figure S1. Color change of anthracene as a function of pressure.
4

Figure S2. Decompression Raman spectra of (a) naphthalene, (b) anthracene, (c) phenahthrene, and (d) pyrene. The periodic modulations are associated with low-amplitude interference patterns from the grating, and illustrate the magnitude of intensity loss associated with compression.
5

Figure S2. Decompression infrared spectra of (a) naphthalene, (b) anthracene, (c) phenahthrene, and (d) pyrene.
6

Table S1. Raman and infrared modes observed at room temperature and pressure (assingments based on Bree and
Kydd, 1970,
Lippincott and O’Reilly, 1955, Person et al., 1955, and
Pimentel et al., 1955, and Mitra and Bernstein,
1959 ) pressure dependences of peak positions, and calculated room pressure and 7 GPa mode Gr ü neisen parameters of naphthalene.
ν
0 i
(cm -1 ) Assignment
(d ν
0 i
/dP)(cm -
1 /GPa) Up to
~3.0 GPa transition
γ i
ν
0 i
>3 GPa
(cm -1 )
(d ν
0 i
/dP) (cm -
1 /GPa) >3
GPa
7 GPa γ i
- Inter-molecular (R) - - 99 6.36 ±0.49 3.10
-
-
75
110
124
388
392
464
509
513
618
724
757
763
777
790
846
960
-
976
Inter-molecular (R)
Inter-molecular (R)
Inter-molecular (R)
Inter-molecular (R)
Inter-molecular (R)
O-O-P ring bending (R)
O-O-P C-C bending (R)
O-O-P C-C bending (R)
C-C stretching (R)
I-P ring bending
(R)
I-P ring bending
(IR)
O-O-P C-H bending (R)
Ring breathing (R)
I-P ring bending
(R)
O-O-P ring bending (IR)
O-O-P C-H bending (IR)
O-O-P ring bending (IR)
O-O-P C-H bend
(IR)
O-O-P C-H bend
(IR)
Ring breathing (IR)
-
-
22.64 ±1.08
24.96 ±3.97
30.99 ±4.44
3.79 ±0.29
6.22 ±0.44
2.24 ±0.19
2.09 ±0.12
3.77 ±0.34
0.52 ±0.22
4.21 ±0.46
5.54 ±0.94
5.70 ±0.63
2.80 ±0.22
2.76 ±0.33
4.50 ±0.50
2.26 ±0.14
-
3.16 ±0.29
-
-
1.96
1.48
1.62
0.06
0.10
0.03
0.03
0.05
0.01
0.04
0.05
0.05
0.02
0.02
0.03
0.02
-
0.02
105
133
141
184
216
400
411
472
515
525
620
737
774
781
788
801
863
968
978
988
9.21 ±2.39
8.11 ±0.37
5.75 ±0.50
9.97 ±0.38
8.77 ±0.63
2.75 ±0.04
3.42 ±0.13
2.15 ±0.07
1.11 ±0.03
1.94 ±0.07
0.88 ±0.02
2.66 ±0.10
1.68 ±0.19
3.26 ±0.14
2.36 ±0.07
1.14 ±0.04
3.28 ±0.07
2.15 ±0.01
1.13 ±0.04
3.32 ±0.06
4.23
2.94
1.97
2.61
1.96
0.33
0.40
0.22
0.10
0.18
0.07
0.17
0.10
0.20
0.14
0.07
0.18
0.11
0.06
0.16
7

3022
3029
3050
-
-
3056
3062
3068
1167
1504
1593
3004
3006
981
1008
1017
1146
Ring breathing (IR)
I-P C-H bending
(IR)
Ring breathing (R)
I-P C-H bend (R)
O-O-P C-H bend
(R)
C-C stretch (IR)
C-C stretch (IR)
C-H stretch (IR)
C-H stretch (R)
C-H stretch (IR)
C-H stretch (IR)
C-H stretch(IR)
C-H stretch (R)
C-H stretch (R)
C-H stretch (R)
C-H stretch (IR)
C-H stretch (IR)
3.41 ±0.38
0.80 ±0.23
3.26 ±0.29
3.09 ±0.44
3.29 ±0.59
2.74 ±0.29
2.04±0.21
3.75 ±0.68
5.28 ±1.01
3.52 ±0.36
4.39 ±0.36
4.12 ±0.41
-
-
12.16 ±1.07
6.79 ±1.24
6.81 ±0.79
0.01
0.01
0.01
-
-
0.03
0.01
0.01
0.02
0.01
0.01
0.01
0.01
0.02
0.01
0.02
0.02
3.64 ±0.07
2.05 ±0.05
3.61 ±0.09
2.80 ±0.12
3.89 ±0.14
1.85 ±0.04
1.82 ±0.04
4.19 ±0.08
4.26 ±0.29
4.34 ±0.07
-
4.57 ±0.33
4.34 ±0.32
6.61 ±0.43
8.16 ±0.39
-
5.08 ±0.12
3036
-
3065
3060
3070
3094
-
3091
1180
1514
1601
3021
3025
994
1013
1028
1157
0.07
-
0.07
0.07
0.10
0.13
-
0.08
0.16
0.06
0.05
0.07
0.07
0.18
0.10
0.17
0.12
8

Table S2. Raman and infrared modes observed at room temperature and pressure (assingments based on Califano
1962, Abasbegovic et al., 1964, and Räsänen et al., 1972 ) pressure dependences of peak positions, and calculated mode Gr ü neisen parameters of anthracene at room pressure and 7 GPa. *only two data points.
ν
0 i
(cm-1) Assignment
(d ν
0 i
/dP)(cm-
1/GPa) Up to ~2.9
GPa transition
γ i
ν
0 i
3-7 GPa
(cm -1 )
(d ν
0 i
/dP)
(cm -1 /GPa)
3-7 GPa
7 GPa γ i
-
-
72
124
241
243
286
290
391
393
395
476
479
520
601
623
625
654
725
737
-
744
748
Inter-molecular (R)
Inter-molecular (R)
Inter-molecular (R)
Inter-molecular (R)
O-O-P C-C bend (R)
O-O-P C-C bend (R)
O-O-P C-C bend (R)
O-O-P C-C bend (R)
C-C stretching (R)
C-C stretch and bend
(R)
I-P C-C bend (R)
C-C stretching (R)
O-O-P C-C bend (R)
I-P C-C bend (R)
Ring bending (IR)
C-C stretching (R)
C-C stretching (R)
B
1u
(IR)
O-O-P C-H bend (IR)
B
3u
(IR)
(IR)
Skeletal deformation
(IR)
O-O-P C-H bending (R)
-
-
20.11 ±2.67
23.92 ±2.39
6.70 ±0.54
8.46 ±0.73
11.81 ±0.97
13.80 ±1.07
1.67 ±0.19
1.93 ±0.12
4.50 ±0.26
2.37 ±0.25
4.54 ±0.54
1.49 ±0.34
2.02 ±0.17
1.16 ±0.15
1.26 ±0.12
1.77 ±0.14
3.38 ±0.24
2.19 ±0.23
-
3.63 ±0.15
3.52 ±0.54
-
-
2.09
1.45
0.21
0.26
0.31
0.36
0.03
0.04
0.09
0.04
0.07
0.02
0.03
0.01
0.02
0.02
0.04
0.02
-
0.04
0.04
84
98
131
202
223
264
-
-
-
400
411
-
-
525
609
-
-
662
737
-
752
757
-
5.31 ±1.42
7.62 ±1.25
8.13 ±1.18
9.82 ±1.95
11.79 ±1.01
3.37 ±0.19
-
-
-
1.75 ±0.54
3.33 ±0.84
-
-
0.22 ±0.05
1.56 ±0.11
-
-
1.59 ±0.17
3.20 ±0.43
-
1.98 ±0.23
3.68 ±0.32
-
3.58
4.40
3.51
2.75
2.99
0.72
-
-
-
0.25
0.46
-
-
0.02
0.14
-
-
0.14
0.25
-
0.15
0.28
-
9

956
-
979
998
-
1008
1164
1171
1187
1252
753
760
810
-
860
883
-
906
915
917
956
1260
1275
1398
1448
1481
1507
1534
I-P C-C bending (R)
C-C stretch and bend
(R)
B
2u
(IR)
(IR)
B
3u
(IR)
O-O-P C-H bend (IR)
O-O-P C-H bend (IR)
Ring bending (IR)
O-O-P C-H bend (R)
O-O-P C-H bend (R)
C-C stretching (R)
C-H OOP bend (IR)
C-H OOP bend (IR)
B
3u
(IR)
I-P C-H bend (IR)
I-P C-H bend (IR)
I-P C-H bend (R)
I-P C-H bend (R)
C-C stretch and bend
(R)
I-P C-H bend (R)
C-C stretch and bend
(R)
C-C stretch (R)
O-O-P C-H bend (R)
Ring stretching (IR)
Ring stretching (IR)
C-C stretching (R)
C-C stretching (R)
Ring stretching (IR)
2.18 ±0.14
-
4.68 ±0.25
2.83 ±0.20
-
3.58 ±0.16
1.55 ±0.12
3.17 ±0.16
2.81 ±0.16
7.11 ±1.08
3.17 ±0.20
4.68 ±0.36
3.60 ±0.33
-
5.33 ±0.40
3.14 ±0.24
-
1.92 ±0.16
1.73 0.35
2.54 ±0.24
3.17 ±0.22
5.10 ±0.22
3.45 ±0.22
5.23 ±0.34
3.34 ±0.14
3.27 ±0.18
4.98 ±0.39
3.59 ±0.28
0.02
-
0.04
0.02
-
0.03
0.01
0.02
0.02
0.04
0.03
0.05
0.03
-
0.05
0.03
-
0.02
0.01
0.02
0.02
0.03
0.02
0.03
0.02
0.02
0.02
0.02
0.07
0.11
0.23
0.17
0.15
-
0.06
-
0.08
0.14
0.16
0.14
0.22
0.25
-
-
-
0.28
0.17
0.15
0.15
0.22
-
0.16
0.07
-
-
0.09
1.15 ±0.10
1.95 ±0.30
4.11 ±0.45
3.07 ±0.29
2.70 ±0.22
-
1.18 ±0.30
-
1.70 ±0.12
3.17 ±0.87
2.12 ±0.57
1.98 ±0.66
3.13 ±0.26
3.80 ±0.33
4.28 ±0.36
2.64 ±0.19
2.33 ±0.29
2.40 ±0.18
-
-
-
4.86 ±0.85
-
3.88 ±0.22
1.75 ±0.14
-
-
2.32 ±0.20
964
970
995
1008
1014
-
1169
-
1197
1274
765
775
822
873
-
-
-
878
895
906
913
1279
-
1417
1455
-
-
1544
10

1551
1557
1621
1629
1634
1786
3005
3010
3023
3028
3049
-
3050
3054
3054
3071
3076
1797
1809
2850
2919
2988
C-C stretch and bend
(R)
C-C stretching (R)
Ring stretching (IR)
C-C stretch and bend
(R)
C-C stretching (R)
(IR) 1 st Overtone of
906?
(IR) Combination
860+936
B
1u
(IR)
C-H stretch (IR)
C-H stretch (IR)
C-H stretch (IR)
C-H stretch (R)
C-H stretch (IR)
C-H stretch (IR)
C-H stretch (R)
C-H stretch (R)
C-H stretch (IR)
C-H stretch (IR)
C-H stretch (IR)
C-H stretch (R)
C-H stretch (R)
C-H stretch (R)
5.04 ±0.45
5.78 ±0.80
3.48 ±0.21
4.98 ±0.39
3.70 ±0.80
9.85 ±0.63
4.01*
2.38*
4.96 ±0.31
11.53 ±0.71
5.63 ±0.29
6.28 ±0.55
6.27 ±0.88
7.75 ±0.47
8.09 ±0.36
9.77 ±0.59
-
7.26 ±0.56
11.69 ±0.99
10.91 ±0.86
6.96 ±0.27
8.75 ±0.15
0.02
0.03
0.02
0.02
0.02
0.04
0.02
0.02
0.02
0.02
0.02
-
0.02
0.03
0.03
0.02
0.02
0.02
0.01
0.01
0.03
0.01
0.10
-
0.10
-
-
-
-
0.12
0.13
0.11
-
0.12
-
0.18
0.13
-
-
-
-
0.15
-
-
2.86 ±0.33
-
2.91 ±0.20
-
-
-
-
-
7.48 ±1.30
-
-
-
6.65 ±0.48
7.23 ±0.78
5.89 ±0.72
-
6.75 ±0.50
-
9.59 ±1.19
7.22 ±1.59
-
-
1567
-
1633
-
-
-
-
3022
3050
3058
-
3062
-
3096
3093
-
-
-
-
2870
-
-
11

Table S3. Raman and infrared modes observed at room temperature and pressure (assingments based on Bree et al.,
1972, Godec and Colombo, 1976, and Schettino et al. 1966) pressure dependences of peak positions, and calculated mode Gr ü neisen parameters of phenanthrene at room pressure and 7 GPa.
ν
0 i
(cm-1) Assignment
(d ν
0 i
/dP)
(cm-1/GPa)
Up to ~3.0
GPa transition
γ i
ν
0 i
> 5 GPa(cm-1)
(d ν
0 i
/dP)
(cm-1/GPa)
>5 GPa
7 GPa γ i
-
-
73
106
124
237
252
401
412
426
443
Intermolecular
(R)
Intermolecular
(R)
Inter-molecular
(R)
Inter-molecular
(R)
Inter-molecular
(R)
C-C-C bending
(R)
C-C-C-C torsion
(R)
C-C-C-C torsion
(R)
C-C-C bending
(R)
C-C-C bending
(R)
C-C-C-C torsion
(R)
-
-
-
-
15.44 ±2.25 1.59
18.57 ±1.56 1.31
23.79 ±3.85 1.44
6.67 ±0.06
7.67 ±0.50
-
4.55 ±0.43
3.32 ±0.23
4.41 ±0.18
0.21
0.23
-
0.08
0.06
0.07
82
98
131.08
193.54
211.24
266.85
289.98
414.22
428.50
440.01
-
4.68 ±0.69
6.32 ±0.08
7.46 ±0.28
8.99 ±0.67
10.73 ±0.68
5.32 ±0.47
10.13 ±0.33
2.51 ±0.14
1.92 ±0.12
5.59 ±0.36
-
6.27
7.09
6.26
5.10
5.58
2.19
3.84
0.67
0.49
1.40
-
494 0.02 - - -
498
535
548
584
615
618
710
712
716
(R) 498 observed 1.55 ±0.04
C-C-C bending
(R)
(R) Observed not assigned
C-C-C bending
(R)
C-C-C bending
(R)
C-C-C bending
(R)
C-C-C bending
(R)
H-C-C-C OOP bending (R)
C-C-C bending
(R)
2.73 ±0.02
2.35 ±0.04
1.43 ±0.83
1.55 ±0.04
0.97 ±0.05
1.36 ±0.21
1.88 ±0.20
2.48 ±0.50
?(R) 3.11 ±0.40
0.04
0.03
0.02
0.02
0.01
0.02
0.02
0.03
0.03
-
-
554.49
-
-
623.64
717.77
722.16
729.17
-
-
1.51 ±0.07
-
-
0.78 ±0.13
0.98 ±0.17
2.24 ±0.12
3.04 ±0.52
-
-
0.30
-
-
0.14
0.15
0.34
0.46
12

733
762
792
823
829
836
875
945
952
1001
1036
1038
1039
1164
1173
1202
1226
1246
1428
1456
1503
1526
1574
1600
1617
1628
C-C-C bending
(IR)
H-C-C-C OOP bending (R)
H-C-C-C OOP bending (IR)
C-C-C bending(IR)
C-C-C bending
(R)
Ring def (IR)
H-C-C-C OOP bending (IR)
H-C-C-C OOP bending (IR)
H-C-C-C OOP bending (IR)
C-H bend (IR)
2.70 ±0.26
3.22 ±0.40
1.27 ±0.11
4.09 ±0.56
2.04 ±0.33
2.66 ±0.29
3.03 ±0.10
0.92 ±0.19
2.58 ±0.30
1.90 ±0.25
C-C stretch + H-
C-C bending (R)
C-C stretching
(R)
C-C stretch + H-
C-C bending
(IR)
C-C stretch + H-
C-C bending (R)
H-C-C-C OOP bending (R)
C-C stretch + H-
C-C bending (R)
1348-115=1233
(R)
H-C-C bending
(R)
C-C stretch + H-
C-C bending
(IR)
C-C stretch + H-
C-C bending
(IR)
C-C stretch + H-
C-C bending
(IR)
1.99 ±0.06
-
1.98 ±0.27
3.12 ±0.01
6.32 ±0.61
5.89 ±0.54
-
2.89 ±0.67
3.54 ±0.45
2.42 ±0.35
3.28 ±0.54
C-C stretch(IR) 2.89 ±0.52
C-C stretch (IR) 3.34 ±0.61
C-C stretch(IR) 3.14 ±0.58
C-H bend (IR)
C-H bend (IR)
3.45 ±0.52
3.96 ±0.77
0.01
0.02
0.01
0.02
0.01
0.02
0.01
0.02
0.02
0.02
0.04
0.04
-
0.02
0.03
0.03
0.01
0.04
0.02
0.02
0.03
0.01
0.02
0.01
0.01
-
13
1466.97
1518.50
1543.22
1590.53
1615.25
1632.99
1649.12
-
-
-
1240.56
1259.47
1445.40
744.62
774.74
798.16
829.70
838.21
841.92
888.99
951.33
964.51
1010.48
1044.39
1053.78
1048.11
0.09
0.16
0.24
0.12
0.13
0.11
0.22
-
-
-
0.49
0.38
0.16
0.26
0.42
0.15
0.20
0.18
0.25
0.16
0.25
0.42
0.26
0.31
0.31
0.17
1.25 ±0.09
2.25 ±0.13
3.43 ±0.40
1.79 ±0.43
1.96 ±0.12
1.57 ±0.36
3.35 ±1.84
1.79 ±0.14
3.00 ±0.05
1.12 ±0.12
1.50 ±0.15
1.38 ±0.05
1.88 ±0.09
1.32 ±0.13
2.21 ±0.31
3.67 ±0.70
2.42 ±0.50
2.91 ±0.18
2.96 ±0.15
1.65 ±0.05
-
-
-
5.52 ±0.21
4.40 ±0.22
2.17 ±0.16

3012
3023
3036
3045
3060
3063
3076
3076
3088
3098
C-H stretch (IR) 6.18 ±0.39
C-H stretch (IR) 5.52 ±0.22
C-H stretch(R) 6.68 ±0.04
C-H stretch (IR) 6.44 ±0.47
C-H stretch(R) 6.52 ±2.61
C-H stretch (IR) 6.04 ±0.56
0.02
0.01
C-H stretch (IR) 11.86 ±0.17 0.03
C-H stretch (R) 11.33 ±0.83 0.03
C-H stretch (R) 11.03 ±0.87 0.03
C-H stretch (IR) 8.94 ±0.73 0.02
0.02
0.01
0.02
0.02
3041.79
3049.64
-
3076.93
-
3097.85
3112.86
3123.86
-
3138.33
8.32 ±2.52
7.93 ±0.34
-
12.56 ±2.42
-
2.52 ±1.13
3.37 ±1.51
8.10 ±0.89
-
8.05 ±2.77
-
0.09
0.12
0.29
-
0.28
0.30
0.29
-
0.45
14

958
964
969
1065
1106
1142
1242
1405
1405
1435
1449
1467
838
840
892
913
676
709
749
820
166
406
457
592
66
76
90
128
Table S4. Raman and infrared modes observed at room temperature and pressure (assingments based on Bree et al.,
1971, and Califano and Abbondanza 1963) pressure dependences of peak positions, and calculated mode Gr ü neisen parameters of pyrene.
ν
0 i
(cm -1 ) Assignment
(d ν
0 i
/dP) (cm-
1/GPa) Up to ~2.0
GPa transition
γ i
Inter-molecular (R)
Inter-molecular (R)
Inter-molecular (R)
Inter-molecular (R)
Inter-molecular (R)
B
1 g
(R)
B
3 g
(R)
A g
(R)
B
1 u
(IR)
C-H deformation (IR)
C-H deformation (IR)
Ring bending (IR)
Ring bending (IR)
B
1 g
(R)
B
1 u
(IR)
B
1 u
(IR)
B
1 u
(IR)
C-H deformation (IR)
B
1 u
(IR)
A g
(R)
B
3 g
(R)
A g
(R)
A g
(R)
(R)
A g
(IR)
Ring stretching (IR)
Ring stretching (IR)
Ring stretching (IR)
11.59 ±1.23
16.01 ±1.91
25.13 ±2.76
23.48 ±2.58
26.19 ±2.59
0.01
0.02
0.01
0.03
0.01
0.01
0.02
0.03
0.06
0.03
0.05
0.01
0.02
0.02
0.02
0.01
0.01
0.02
0.02
0.01
0.01
0.01
0.01
3.71 ±0.31
2.43 ±0.46
4.45 ±2.13
1.26 ±0.17
1.68 ±0.11
2.84 ±0.10
2.32 ±0.29
1.00 ±0.23
1.08 ±0.53
2.67 ±0.11
2.43 ±0.40
1.85 ±0.32
2.48 ±0.25
2.17±0.57
5.21 ±0.29
2.44 ±0.13
2.43 ±0.28
4.24 ±0.41
6.39 ±0.40
1.67 ±0.27
1.94 ±0.41
2.96 ±0.53
2.26 ±0.54
1.14
1.37
1.81
1.19
1.03
15

1628
1643
3009
3032
3039
3049
3053
3080
1487
1550
1587
1595
1593
1599
B
1 u
(IR)
A g
(R)
B
1 u
(IR)
B
1 u
(IR)
B
3 g
(R)
Ring stretching (IR)
A g
(R)
A g
(R)
C-H stretching (R)
C-H stretching (IR)
C-H stretching (R)
C-H stretching (IR)
C-H stretching (R)
C-H stretching (IR)
3.11 ±0.23
5.29 ±0.42
-
-
5.64 ±0.37
2.06 ±0.24
4.47 ±0.23
3.27 ±0.27
8.23 ±0.64
7.52 ±0.73
19.70 ±10.96
8.63 ±0.51
14.19 ±0.94
11.27 ±0.51
0.02
0.01
0.02
0.02
0.04
0.02
0.03
0.02
0.01
0.02
-
-
0.02
0.01
16